High Output Modular CAES (HOMC)

ABSTRACT

A compressed air energy storage system integrated with a source of secondary heat, such as a simple cycle gas turbine, to increase power production and to provide power regulation through the use of stored compressed air heated by said secondary heat to provide power augmentation.

FIELD OF THE INVENTION

This invention relates to electrical power generating capacity, and morespecifically to energy storage that is useful for providing electricalpower during periods of peak electrical power demand and powerregulation.

BACKGROUND OF THE INVENTION

As demand for electric energy has risen in recent years, in somepopulation centers such as New York City, the difference between thepeak electric power that can be supplied and the peak demand for thatelectric power, referred to as “margin”, has narrowed to the point thata severe anomaly could eliminate that margin altogether. For example, asustained heat wave in New York City can erode that margin to the pointthat “brown-outs” occur, and if the supply of electric power cannot beincreased, or demand outstrips the increased supply, “black-outs” canoccur. To reduce the risk of “brown-outs” and “black-outs”, responsiblepower authorities have tried to locate sufficient power generationcapacity in or near population centers to meet normal electrical demand,and to provide for sufficient transmission grid capacity serving suchareas so that in the event a severe anomaly such as a heat wave doesoccur, additional electrical energy from distant power plants can beprovided to avoid “brown-outs” or “black-outs”, albeit at a substantialcost due to the losses associated with transmission of electricity overlong distances and at high load factors. Unfortunately, in times ofextreme demand, the transmission grid has a limited capacity to provideadditional electric power to population centers such as New York City,and despite years of discussion and a general acceptance of the need toupgrade the transmission grid, if and when additional capacity will beadded remains unclear. In the absence of sufficient transmission gridcapacity to meet severe anomalies, population centers such as New YorkCity must rely on locally generated electrical power to meet thatdemand, thereby avoiding the need to bring that additional electricalpower in over the transmission grid.

While “base-load” generating capacity may be provided by coal-firedpower plants, nuclear power plants, or “combined cycle” gas turbines,generating capacity to meet peak demand is often provided by “simplecycle” gas turbines. As those skilled in the art will readilyappreciate, simple cycle gas turbines produce substantial amounts ofsecondary heat, which is typically exhausted to the atmosphere. Combinedcycle gas turbines also produce secondary heat, although to a lesserextent. As used herein, the term “secondary heat” means heat produced 1)as, or by, a byproduct of the machines, electrical equipment, orindustrial or biological processes that produce it, or 2) as a usefulproduct in machines, electrical equipment, or industrial or biologicalprocesses but which can also be used for a secondary purpose withoutimpairing the function of such machines, electrical equipment, orindustrial or biological processes.

Unfortunately, increasing local electrical power generation capacity byinstalling additional gas turbines to meet demand in times of severeanomalies faces substantial obstacles, the most obvious being cost.While the costs associated with installing “base-load” generation can berecouped by generating and selling electrical power 24 hours a daythroughout the year, the costs associated with installing generatingcapacity to meet peak demand (so called “peakers”) must be recouped overa few hours of operation per day during a few months of the year. Sincethis results in very high costs per megawatt hour of electrical poweractually produced, power authorities are understandably hesitant toinvest in additional peakers where they have other options.

Space is also an issue in population centers such as New York City,where real estate is at a premium. Acquiring sufficient land to build anew power plant while accommodating nearby residential and businessinterests can delay construction of additional power generation capacitylong past the date that additional capacity is needed. Permittingrequirements to achieve acceptable emissions levels can further delayconstruction of additional generating capacity, particularly in denselypopulated areas.

Faced with such cost, space and emissions obstacles, power authoritiesoften resort to the use of existing, less efficient generating capacity.Since this generating capacity is already installed, costs and realestate are not an issue, and in some cases this generating capacity maybe “grand-fathered” in under existing permits. Also, older gas turbinesare generally not as efficient as newer ones, which translates to morewaste heat being given off per megawatt hour being generated. As aresult, use of this generating capacity often produces higher emissions,of carbon monoxide and/or other pollutants such as NOx and ozone, permegawatt hour of power generated than their “base-load” counterparts,which can raise air quality concerns depending upon what time of daythis generating capacity is operated.

Compressed air energy storage (“CAES”) plants have been considered as apotential solution to deal with peak electrical power demands inpopulation centers. In general, these systems store compressed air usingoff-peak electrical power, and then use that compressed air to produceelectrical power at times of peak demand. The air storage for CAESsystems has traditionally been large underground caverns that werepressurized to a maximum pressure, and then bled down until they reachedthe minimum to the operating pressure of the expanders, at which timethe expansion cycle was stopped until the compression cycle was runagain. This type of cyclic duty results in a compression system whereall of the stages of the compressor are always engaged and have arelative constant exit condition. For example, Dresser-Rand's“SmartCAES” system, which is shown schematically in FIGS. 1A and 1B,uses single or multiple multi-stage intercooled compressors 101A, 101B,101C, 101D, 101E, 101F, 101G to produce compressed air that is stored inan air storage cavern 107, and multi-stage expanders 102A, 102B, 102C,102D, 102E, 102F to expand the compressed air, in which the compressionand expansion equipment are separate systems. In typical CAES systems, arecuperator 108 is used to transfer heat from the exhaust gas 103 of anexpander 102F to the compressed air as it exits the air storage cavern107. The recuperator 108 preheats the compressed air before it enters adedicated high pressure combustor 106. There, fuel 110 is added andcombusted, to further heat the compressed air before it is fed into ahigh pressure expander 102A. The compressed air exiting the highpressure expander 102C is then reheated in a low pressure combustor 109,where more fuel 112 is added and combusted, prior to being fed into alow pressure expander 102D. The electrical power produced by theexpanders of the SmartCAES is normally the product of diffusioncombustion in the high and low pressure combustors 106, 109, withrelatively high emissions which require a selective catalytic reducer(“SCR”) (114) to meet common emission requirements (although some maynow be operating with premixed combustion systems). In addition, sincethe SmartCAES systems are designed to have either 110 MW or 135 MW plantoutput ratings, either large natural caverns 107 must be available nearthe site of each SmartCAES installation, or the geology at the SmartCAESplant site must be suited for development of a cavern with the requiredcharacteristics. Therefore, locations for use of the SmartCAES systemare limited by local geological conditions.

FIGS. 2A and 2B schematically show Energy Storage & Power's “CAES2”system, in which multiple multi-stage intercooled compressors 201A,201B, 201C, 201D, 201E, 201F, 201G are used to produce compressed airthat is stored in long air storage pipes, porous geological media orcaverns 208. In the CAES2 system, a recuperator 206 is used to transferheat from the exhaust gas of a gas turbine 207 to the compressed airprior to entering multi-stage expanders 202A, 202B, 202C, 202D, 202E,202F. Depending on the particular system, partially expanded compressedair 203, specifically limited to that which can be bled from between thefirst and second expander stages 202A, 202B, may be taken off anddelivered to the gas turbine's combustor 204 for power augmentation, orthe compressed air may be expanded through all stages of the expanders202A, 202B, 202C, 202D, 202E, 202F and then delivered directly to theinlet 205 of the gas turbine 207 as chilled air for power augmentation,provided that the air is below ambient temperature so as to be suitablefor inlet cooling (see U.S. Pat. Nos. 5,934,063, 6,038,849, 6,134,893,6,244,037, 6,305,158). These patented systems have recuperators 206, topreheat the air before it enters the expander 202A, and as a result,very hot compressed air is fed into the first stage of the expander202A, often within 50° F. of the temperature of the gas turbine'sexhaust gas. This very hot, compressed air is then expanded to ambientpressure in a manner such that the temperature of the compressed airdoes not go below freezing, to prevent icing issues in either theexpander stages, or the gas turbine inlet. About 40% of the rated poweroutput of a CAES2 plant is produced by the gas turbine 207 that isincluded with the system, and the remaining power comes from thegenerator 209 that is driven by the expanders 202A, 202B, 202C, 202D,202E, 202F. The emissions of the CAES2 system are typically lower thanthose produced by the SmartCAES system due to incorporation of a gasturbine having a premix combustion system, and although the use of pipesfor air storage 208 can allow the CAES2 system to be installed atlocations that do not have existing caverns, the quantity of pipesneeded by the CAES2 system increases the cost of installing a CAES2system to the point that many power authorities may feel is prohibitive.

What is needed is a means of providing additional local electrical powerduring peak demand periods which does not necessitate the purchase ofsubstantial quantities of additional land, can meet existing emissionsrequirements, has a high “round trip electrical efficiency” (i.e. energyoutput/energy input) and is cost-competitive as compared with otheroptions.

BRIEF SUMMARY OF THE INVENTION

One advantage of the present embodiment is the ability to construct thesystem on a mobile platform capable of being transported in whole or inpieces.

Another advantage of the present embodiment is to provide localelectrical power generation during peak demand periods which does notnecessitate the purchase of substantial quantities of additional land.

Another advantage of the present embodiment is the ability to providelocal electrical power generation, during peak demand periods, that canmeet existing emissions requirements for operation during such periods.

Another advantage of the present embodiment is the ability to providemore megawatt hours of energy to the electrical grid than is consumedduring the storage process, where waste heat is not considered.

Another advantage of the present embodiment is to provide localelectrical power generation during peak demand periods that iscost-competitive as compared with other options.

Accordingly, an embodiment of the present invention is an energy storageand retrieval system for obtaining useful work from a source of heat,the system comprising means for producing compressed air, means forstoring said compressed air, means for extracting work from thecompressed air including a plurality of expanders, a plurality of firstconduits, and a plurality of second conduits, each of the expandershaving an inlet and an outlet, each of the first conduits connected toone of the inlets of the plurality of expanders to deliver thecompressed air thereto, and each of the second conduits connected to oneof the outlets of the plurality of expanders to receive the compressedair therefrom; and, means for transferring energy between the compressedair and a heat transfer fluid, including a first manifold, and a firstplurality of heat exchangers, including an initial heat exchanger and aplurality of downstream heat exchangers, each of the first plurality ofheat exchangers having a first heat exchange circuit including a firstinlet and a first outlet, and a second heat exchange circuit including asecond inlet and a second outlet, each of the first outlets of the firstplurality of heat exchangers connected to one of the first conduits todeliver the compressed air thereto, each of the first inlets of theplurality of downstream heat exchangers connected to one of the secondconduits to receive the compressed air therefrom, and each of the secondinlets of the plurality of heat exchangers connected to the firstmanifold; wherein the energy is heat from the source of heat, and thefirst manifold is connected to the source of heat to receive the heattransfer fluid therefrom for transferring the energy to the compressedair.

More specifically, a present embodiment provides a compression circuitthat has a plurality of compressor stages to compress air, with coolingof the compressed air between stages, and is operated in such a way toobtain a highly efficient compression process with changing exitpressure conditions to produce compressed air that is stored, preferablyin high pressure tanks, and an expansion circuit that has a plurality ofexpander stages to expand the compressed air, with heat exchangersbetween expander stages to reheat the compressed air to a predeterminedtemperature using secondary heat from a source, such as the exhaust ofan existing gas turbine.

Also, a present embodiment is an apparatus that comprises an energystorage and retrieval system for obtaining useful work from an existingsource of secondary heat, comprising a source of compressed air, atleast one generator, a plurality of expander stages, each of theplurality of expander stages having an inlet and an outlet, at least aportion of the plurality of expander stages having an outlet flowcontrol, and each of the plurality of expander stages is connected tothe generator. The present embodiment also includes a first manifold,and a first plurality of heat exchangers, including an initial heatexchanger and a first plurality of downstream heat exchangers, whereeach of the first plurality of heat exchangers has a first heat exchangecircuit and a second heat exchange circuit, and each of the first heatexchange circuits of the first plurality of downstream heat exchangersis in selective fluid communication with one of the outlets of theplurality of expander stages through one of the outlet flow controls ofthe plurality of expander stages, and each of the second heat exchangecircuits of the first plurality of heat exchangers is in fluidcommunication with the first manifold, and the first manifold is influid communication with the source of secondary heat to receivesecondary heat therefrom.

The present embodiment uses high pressure air storage tanks, inconjunction with heating of the compressed air between expander stages,which substantially reduces the volume of compressed air that needs tobe stored for a given megawatt-hours of energy output. Therefore, thecost of providing the air storage (for those power plants that are notlocated near a natural cavern) is reduced compared to the air storagedevices used in the prior art, while the use of secondary heat from anexisting source allows the present embodiment to meet local emissionsrequirements.

A present embodiment of the invention uses the same heat exchangers toperform both the cooling of the compressed air between stages of thecompression circuit and the heating of the compressed air between stagesof the expansion circuit to further reduce the capital cost ofimplementing the present embodiment as a solution for peak electricpower demand at those sites where compression and expansion of air doesnot need to be performed simultaneously. Additionally, for an existinggas turbine located on a site adjacent a navigable waterway, the presentinvention may be incorporated into a barge that can be anchored adjacentsuch site, thereby avoiding the costs of acquiring land on which toplace additional generating capacity.

Other advantages, features and characteristics of the present invention,as well as the methods of operation and the functions of the relatedelements of the structure and the combination of parts will become moreapparent upon consideration of the following detailed description andappended claims with reference to the accompanying drawings, all ofwhich form a part of this specification.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are a schematic drawing of a compressed air energystorage system of the prior art.

FIGS. 2A and 2B are a schematic drawing of another compressed air energystorage system of the prior art.

FIGS. 3A and 3B are a schematic drawing of the present embodiment inwhich the source of secondary heat is a simple cycle gas turbine.

FIGS. 4A and 4B are a schematic drawing of the first alternateembodiment in which the source of secondary heat is a simple cycle gasturbine.

FIGS. 5A and 5B are a schematic drawing of the second alternateembodiment in which the source of secondary heat is a simple cycle gasturbine.

FIG. 6 is a schematic drawing of the HOMC system integrated with a steamcycle of a combined cycle power plant.

FIG. 7 is a schematic drawing of the HOMC system where the heat issupplied by an electric source coming from a photovoltaic solar plant.

FIG. 8 is a graphical comparison of the output characteristics of a HOMCsystem in regulation mode compared to a battery.

FIG. 9 is a schematic drawing of the HOMC system with direct firedburners as the heat source.

FIG. 10 is a graphical representation of a combined waste removal,energy storage and produce delivery system.

DETAILED DESCRIPTION OF THE INVENTION

The components of preferred embodiment of the high output modularcompressed air energy storage system (“HOMC”) of the present inventionare shown schematically in FIGS. 3A and 3B, as they are used with anexisting gas turbine 301. In this embodiment, the same heat exchangersused to produce the compressed air that is delivered to the air storageare used in the process of expanding that compressed air to produceelectricity. The preferred embodiment is useful where the compressionprocess and the expansion processes are run at separate times, as is thecase for typical compressed air energy storage.

More specifically, the preferred embodiment of the present inventionincludes a plurality of 3C1, 3C2, 3C3, 3C4, 3C5, 3C6, 3C7, compressorstages, which may be either centrifugal or axial depending on theparticular cost targets and efficiencies desired, for producingcompressed air from ambient air 302, an air storage 303 for storage andretrieval of the compressed air, a plurality of expander stages 3E1,3E2, 3E3, 3E4, 3E5, 3E6 for driving a generator 304 from expansion ofthe compressed air, a regulator 305 for selectively controlling thepressure at which compressed air is released from the air storage, ahydraulic tank 306 and high pressure pump 307 for selectively fillingthe air storage with hydraulic fluid, preferably water, as described ingreater detail below with respect to the present embodiment of theinvention. As used herein, the term “air storage” means one or moretanks, pipes or other storage device of the type known in the art whichcan receive, retain, and deliver compressed air.

Each of the compressor stages 3C1, 3C2, 3C3, 3C4, 3C5, 3C6, 3C7 isdriven by an electric motor 308 (preferably all of the plurality ofcompressor stages are driven by a single electric motor), and theexpander stages 3E1, 3E2, 3E3, 3E4, 3E5, 3E6 collectively drive a singlegenerator 304. As those skilled in the art will readily appreciate, theelectric motor 308 and generator 304 described in the present inventionmay be a single combined motor/generator of the type that is known inthe art, and the compressor stages 3C1, 3C2, 3C3, 3C4, 3C5, 3C6, 3C7 andexpander stages 3E1, 3E2, 3E3, 3E4, 3E5, 3E6 may be mounted on commonshafts 309, 310 with clutch systems on the motor/generator between thecompressor shaft 309 and the expander shaft 310 to allow themotor/generator to 1) independently drive the compressor stages withoutdriving, or being driven by, the expander stages, 2) be driven by theexpander stages without driving the compressor stages, or 3) drive thecompressor stages while being driven by the expander stages in certainembodiments of the present invention. In addition, the present inventionincludes circulation pumps 311, 312, a plurality of heat exchangers3HE1, 3HE2, 3HE3, 3HE4, 3HE5, 3HE6, 3HE7 for transferring heat betweenthe compressed air 314, the exhaust gas of the gas turbine 301, and acooling source, such as a cooling tower 315, and the piping and valvesnecessary to interconnect the above-mentioned components. While thepresent invention is described in terms of centrifugal compressor stagesand the flow control valves that control the flow of compressed airtherethrough, it is to be understood that if axial flow compressorstages with variable inlet guide vanes and variable exit guide vaneswere used, flow control may be accomplished with these as well. As usedherein, a “flow control” means a valve or any mechanical device by whichthe flow of a fluid, either liquid or gas, may be selectively started,stopped, or regulated by a movable part that opens, shuts, or partiallyobstructs one or more ports or passageways.

As those skilled in the art will readily appreciate, each of thecompressor stages 3C1, 3C2, 3C3, 3C4, 3C5, 3C6, 3C7 has an inlet throughwhich air is received, and an outlet through which the air exits at ahigher pressure and higher temperature. Conversely, each of the expanderstages 3E1, 3E2, 3E3, 3E4, 3E5, 3E6 has an inlet through whichcompressed air is received, and an outlet through which the air exits ata lower pressure and lower temperature. Further, as shown in FIGS. 3Aand 3B, each of the heat exchangers 3HE1, 3HE2, 3HE3, 3HE4, 3HE5, 3HE6,3HE7 has a first heat transfer circuit with an inlet and an outlet, anda second heat transfer circuit with an inlet and an outlet. The airstorage tank 303, which is comprised of a plurality of high pressure gasstorage cylinders manifolded together, also includes an inlet 316 and anoutlet 317.

As shown in FIGS. 3A and 3B, one of the heat exchangers 318 is inthermal contact with a heat source, for example, located inside the gasturbine exhaust manifold to receive heat from the hot exhaust gasexiting the gas turbine 301. That heat is then transferred to a heattransfer medium, preferably water and/or steam (collectively referred toherein as “hot water”), that is circulated through the exhaust gas heatexchanger 318 to receive heat therefrom. The water and/or steam is soheated and is used to provide heat to the compressed air as it passesthrough the heat exchangers, as described below. Another one of the heatexchangers, the pre-heater 319 is in thermal contact with the hotdischarge gas that exits from the low pressure expander stage 3E6 toreceive heat therefrom. This discharge gas heat exchanger (319), whichis used as a pre-heater for the compressed air exiting the air storage,then transfers heat thereto. While this discharge gas heat exchanger isoptional, its inclusion in the present invention minimizes the amount ofsecondary heat needed from the gas turbine, and cools the hot dischargegas that exits from the low pressure expander stage 3E6 before it isdischarged to the atmosphere 320. While the present invention isdescribed herein with respect to a system having seven compressor stagesand six expander stages, those skilled in the art will readilyappreciate that the actual quantities of compressor stages and expanderstages depends on the specific application and cost optimization forwhich the HOMC is to be used.

The preferred embodiment of the present invention includes a compressioncircuit, an expansion circuit, a heat transfer circuit, and an airstorage circuit. The compression circuit is made up of the compressorstages 3C1, 3C2, 3C3, 3C4, 3C5, 3C6, 3C7, the electric motor/generatorthat drives the compressor stages 304, 308, and the piping and flowcontrol valves that carry the air as it is compressed from ambient 302and delivered to the air storage 303. The expansion circuit is made upof the expander stages 3E1, 3E2, 3E3, 3E4, 3E5, 3E6, (which may beeither centrifugal or axial depending on the particular cost targets,desired temperatures, and efficiencies desired), the electric generator304 that is driven by the expander stages 3E1, 3E2, 3E3, 3E4, 3E5, 3E6,and the piping and flow control valves that carry the compressed air asit is expanded from the air storage 303 to ambient pressure 320. Theheat transfer circuit is made up of the heat exchangers 3HE1, 3HE2,3HE3, 3HE4, 3HE5, 3HE6, 3HE7, a heat transfer fluid supply line 352, anda heat transfer fluid return line 354, a heat transfer fluid supplymanifold 347, a heat transfer fluid return manifold 348, a coolantsupply line 349, and a coolant return line 84. The air storage circuitincludes the air storage 303, the high pressure hydraulic pump 307, thewater tank 306 which holds the hydraulic fluid pumped by the hydraulicpump 307, which is preferably water, and the piping and flow controlvalves that carry the hydraulic fluid as it is flows to and from the airstorage 303, as described below.

Referring to FIGS. 3A and 3B, a first compression conduit 321 connectsthe outlet 3C1O of the first compressor stage 3C1 to the inlet 10 of thefirst circuit 11 of the first heat exchanger 3HE1. The first compressionconduit 321 also includes a first air flow control valve 322 to controlthe flow of compressed air through the first compression conduit 321. Asecond compression conduit 323 connects the outlet 12 of the firstcircuit 11 of the first heat exchanger 3HE1 to the inlet 3C2I of thesecond compressor stage 3C2, and the second compression conduit 323includes a second air flow control valve 324.

A third compression conduit 325 connects the outlet 3C2O of the secondcompressor stage 3C2 to the inlet 16 of the first circuit 17 of thesecond heat exchanger 3HE2, and the third compression conduit 325includes a third air flow control valve 326. A fourth compressionconduit 327 connects the outlet 18 of the first circuit 17 of the secondheat exchanger 3HE2 to the inlet 3C3I of the third compressor stage 3C3,and the fourth compression conduit 327 includes a fourth air flowcontrol valve 328.

A fifth compression conduit 329 connects the outlet 3C3O of the thirdcompressor stage 3C3 to the inlet 22 of the first circuit 23 of thethird heat exchanger 3HE3, and the fifth compression conduit 329includes a fifth air flow control valve 330. A sixth compression conduit331 connects the outlet 24 of the first circuit 23 of the third heatexchanger 3HE3 to the inlet 3C4I of the fourth compressor stage 3C4, andthe sixth compression conduit 331 includes a sixth air flow controlvalve 332.

A seventh compression conduit 333 connects the outlet 3C4O of the fourthcompressor stage 3C4 to the inlet 28 of the first circuit 29 of thefourth heat exchanger 3HE4, and the seventh compression conduit 333includes a seventh air flow control valve 334. An eighth compressionconduit 335 connects the outlet 30 of the first circuit 29 of the fourthheat exchanger 3HE4 to the inlet 3C5I of the fifth compressor stage 3C5,and the eighth compression conduit 335 includes an eighth air flowcontrol valve 336.

A ninth compression conduit 337 connects the outlet 3C5O of the fifthcompressor stage 3C5 to the inlet 34 of the first circuit 35 of thefifth heat exchanger 3HE5, and the ninth compression conduit 337includes a ninth air flow control valve 338. A tenth compression conduit338 connects the outlet 36 of the first circuit 37 of the fifth heatexchanger 3HE5 to the inlet 3C6I of the sixth compressor stage 3C6, andthe tenth compression conduit 338 includes a tenth air flow controlvalve 340.

An eleventh compression conduit 341 connects the outlet 3C6O of thesixth compressor stage 3C6 to the inlet 40 of the first circuit 41 ofthe sixth heat exchanger 3HE6, and the eleventh compression conduit 341includes an eleventh air flow control valve 342. A twelfth compressionconduit 343 connects the outlet 42 of the first circuit 41 of the sixthheat exchanger 3HE6 to the inlet 3C7I of the seventh compressor stage3C7, and the twelfth compression conduit 343 includes a twelfth air flowcontrol valve 344.

A thirteenth compression conduit 345 connects the outlet 3C7 of theseventh compressor stage 3C7 to the inlet 46 of the first circuit 47 onthe seventh heat exchanger 3HE7, and the thirteenth compression conduit345 includes a thirteenth air flow control valve 346.

Referring again to FIGS. 3A and 3B, the present invention includes aheat transfer fluid supply manifold 347 and a heat transfer fluid returnmanifold 348. With respect to each of the heat exchangers 3HE1, 3HE2,3HE3, 3HE4, 3HE5, 3HE6, 3HE7 having the outlet of one of the compressorstages 3C1, 3C2, 3C3, 3C4, 3C5, 3C6, 3C7 connected by a compressionconduit to the inlet of the first circuit thereof, as described above,the inlet 13, 19, 25, 31, 37, 43, 49 of the second circuit 14, 20, 26,32, 38, 44, 50 of each of those heat exchangers is connected by a supplyconduit 450, 452, 454, 456, 458, 460, 462 to the heat transfer fluidsupply manifold 347, and the outlet 15, 21, 27, 33, 39, 45, 51 of thesecond circuit 14, 20, 26, 32, 38, 44, 50 of each of those heatexchangers is connected by a return conduit 464, 466, 468, 470, 472,474, 476 to the heat transfer fluid return manifold 348. Each of thesupply conduits 450, 452, 454, 456, 458, 460, 462 and each of the returnconduits 464, 466, 468, 470, 472, 474, 476 includes a flow control valve465, 467, 469, 471, 473, 475, 477 to control the flow of a heat exchangefluid therethrough. A coolant supply line 349 connects the coolantsource, preferably a water cooling tower 315, to the coolant inlet 70 ofthe heat transfer fluid supply manifold 347. Included in the coolantsupply line 349 are a coolant circulating pump 311 and a coolant supplyflow control valve 350. Preferably, the coolant circulating pump 311 islocated between the coolant source 315 and the coolant supply flowcontrol valve 350. In addition, a coolant return line 84 connects thecoolant outlet 85 of the heat transfer fluid return manifold 348 to theinlet 83 of the coolant source 315, and included in the coolant returnline is a coolant return flow control valve 351.

Likewise, a heat transfer fluid supply line 352 connects the heatsource, preferably the outlet 87 of the heat exchanger 318 in the gasturbine exhaust case, to the heat transfer fluid inlet 69 of the heattransfer fluid supply manifold 347. Included in the heat transfer fluidsupply line 352 is a heat transfer fluid supply flow control valve 353.In addition, a heat transfer fluid return line 354 connects the heattransfer fluid outlet 88 of the heat transfer fluid return manifold 348to the inlet 86 of the heat exchanger 318 in the gas turbine exhaustcase. Included in the heat transfer fluid return line are a heated watercirculating pump 312 and a heat transfer fluid return flow control valve355. Preferably, the heat transfer fluid circulating pump 312 is locatedbetween the inlet 86 of the heat exchanger 318 in the gas turbineexhaust case and the heat transfer fluid return flow control valve 355.

A compressed air supply line 317 connects an outlet 65 of the airstorage 303 to the inlet 72 of the first circuit 76 of a pre-heater heatexchanger 319, and the compressed air supply line 317 includes an airflow control valve 361 and a pressure regulator 305. A compressed airmanifold 314 is connected to the outlet 71 of the first circuit 76 ofthe pre-heater heat exchanger 319, and the compressed air manifold 310includes six outlets. A first hydraulic line 68 connects the outlet 92of the high pressure hydraulic pump 307 to a hydraulic inlet 66 on thelower portion of the air storage 303, and a flow control valve 67 isincluded in the first hydraulic line 68 to control the flow of hydraulicfluid into and out of the air storage 303. A second hydraulic line 61connects the outlet 60 of the hydraulic tank 306 to the inlet 91 of thehydraulic pump 307, and a third hydraulic line 63 connects the inlet 62of the hydraulic tank 306 to an outlet 93 on the lower portion of theair storage 303, and a flow control valve 64 is included in the thirdhydraulic line 63 to control the flow of hydraulic fluid therethrough.As those skilled in the art will readily appreciate, although the meansfor maintaining the pressure of the compressed air in the air storage303 is described in terms of a hydraulic tank 306, a high pressure pump307, and flow control valves 64, 67, if the present embodiments of theHOMC are used where deep water air storage is available, (e.g. aconcrete tank with one or more orifices near the bottom to allow waterto flow in and out as compressed air from the compressors stages ispumped into and bled out of the top of the concrete tank), such deepwater air storage could substitute for the hydraulic tank 306, highpressure pump 307, and flow control valves 64, 67 shown in FIGS. 3A and3B.

The preferred embodiment of the present invention includes sixcompressed air manifold discharge conduits 363, 365, 367, 369, 371, 373connected to the compressed air manifold 314. A first compressed airmanifold discharge conduit 363 connects the inlet 40 of the firstcircuit 41 of the sixth heat exchanger 3HE6 to the first compressed airmanifold outlet 82, and the first compressed air manifold dischargeconduit 363 includes a first expansion manifold air flow control valve364. A second compressed air manifold discharge conduit 365 connects theinlet 34 of the first circuit 35 of the fifth heat exchanger 3HE5 to thesecond compressed air manifold outlet 81, and the second compressed airmanifold discharge conduit 365 includes a second expansion manifold airflow control valve 366. A third compressed air manifold dischargeconduit 367 connects the inlet 28 of the first circuit 29 of the fourthheat exchanger 3HE4 to the third compressed air manifold outlet 80, andthe third compressed air manifold discharge conduit 367 includes a thirdexpansion manifold air flow control valve 368. A fourth compressed airmanifold discharge conduit 369 connects the inlet 22 of the firstcircuit 23 on the third heat exchanger 3HE3 to the fourth compressed airmanifold outlet 79, and the fourth compressed air manifold dischargeconduit 369 includes a fourth expansion manifold air flow control valve370. A fifth compressed air manifold discharge conduit 371 connects theinlet 16 of the first circuit 17 of the second heat exchanger 3HE2 tothe fifth compressed air manifold outlet 78, and the fifth compressedair manifold discharge conduit 371 includes a fifth expansion manifoldair flow control valve 372. A sixth compressed air manifold dischargeconduit 373 connects the inlet 10 of the first circuit 11 on the firstheat exchanger 3HE1 to the sixth compressed air manifold outlet 77, andthe sixth compressed air manifold discharge conduit 373 includes a sixthexpansion manifold air flow control valve 374.

The present embodiment of the present invention also includes elevenexpansion conduits connected to the expander stages. A first expansionconduit 375 connects the outlet 42 of the first circuit 41 of the sixthheat exchanger 3HE6 to the inlet 3E1I of the first expander stage 3E1,and the first expansion conduit 375 includes a first expansion air flowcontrol valve 376.

A second expansion conduit 377 connects the outlet 3E1O of the firstexpander stage 3E1 to the inlet 34 of the first circuit 35 of the fifthheat exchanger 3HE5, and the second expansion conduit 377 includes asecond expansion air flow control valve 378.

A third expansion conduit 379 connects the outlet 36 of the firstcircuit 35 on the fifth heat exchanger 3HE5 to the inlet 3E2I of thesecond expander stage 3E2, and the third expansion conduit includes athird expansion air flow control valve 380.

A fourth expansion conduit 381 connects the outlet 3E2O of the secondexpander stage 3E2 to the inlet 28 of the first circuit 29 of the fourthheat exchanger 3HE4, and the fourth expansion conduit 381 includes afourth expansion air flow control valve 382.

A fifth expansion conduit 383 connects the outlet 30 of the firstcircuit 29 of the fourth heat exchanger 3HE4 to the inlet 3E3I of thethird expander stage 3E3, and the fifth expansion conduit 383 includes afifth expansion air flow control valve 384.

A sixth expansion conduit 385 connects the outlet 3E3O of the thirdexpander stage 3E3 to the inlet 22 of the first circuit 23 of the thirdheat exchanger 3HE3, and the sixth expansion conduit 385 includes asixth expansion air flow control valve 386.

A seventh expansion conduit 387 connects the outlet 24 of the firstcircuit 23 of the third heat exchanger 3HE3 to the inlet 3E4I of thefourth expander stage 3E4, and the seventh expansion conduit 387includes a seventh expansion air flow control valve 388.

An eighth expansion conduit 389 connects the outlet 3E4O of the fourthexpander stage 3E4 to the inlet 16 of the first circuit 17 of the secondheat exchanger 3HE2, and the eighth expansion conduit 389 includes aneighth expansion air flow control valve 390.

A ninth expansion conduit 391 connects the outlet 18 of the firstcircuit 17 of the second heat exchanger 3HE2 to the inlet 3E5I of thefifth expander stage 3E5, and the ninth expansion conduit 391 includes aninth expansion air flow control valve 392.

A tenth expansion conduit 393 connects the outlet 3E5O of the fifthexpander stage 3E5 to the inlet 10 of the first circuit 11 of the firstheat exchanger 3HE1, and the tenth expansion conduit 393 includes atenth expansion air flow control valve 394.

An eleventh expansion conduit 395 connects the outlet 12 of the firstcircuit 11 on the first heat exchanger 3HE1 to the inlet 3E6I of thesixth expander stage 3E6, and the eleventh expansion conduit 395includes an eleventh expansion air flow control valve 396.

A duct 90 connects the outlet 3E6O of the sixth expander stage 3E6 tothe inlet 74 of the second circuit 75 of the pre-heater 319, and theoutlet 73 of the second circuit 75 of the pre-heater 320 exhausts to theatmosphere. In addition to the foregoing, the preferred embodiment ofthe present invention includes six bypass conduits.

A first bypass conduit 397 connects the outlet 12 of the first circuit11 of the first heat 3HE1 exchanger to the charging line 411 of the airstorage 303, and the first bypass conduit 397 includes a first bypassair flow control valve 398.

A second bypass conduit 399 connects the outlet 18 of the first circuit17 of the second heat exchanger 3HE2 to the charging line 411 of the airstorage 303, and the second bypass conduit 399 includes a second bypassair flow control valve 400.

A third bypass conduit 401 connects the outlet 24 of the first circuit23 of the third heat exchanger 3HE3 to the charging line 411 of the airstorage 303, and the third bypass conduit 401 includes a third bypassair flow control valve 402.

A fourth bypass conduit 403 connects the outlet 30 of the first circuit29 of the fourth heat exchanger 3HE4 to the charging line 411 of the airstorage 303, and the fourth bypass conduit 403 includes a fourth bypassair flow control valve 404.

A fifth bypass conduit 405 connects the outlet 36 of the first circuit35 of the fifth heat exchanger 3HE5 to the charging line 411 of the airstorage 303, and the fifth bypass conduit 405 includes a fifth bypassair flow control valve 406.

A sixth bypass conduit 407 connects the outlet 42 of the first circuit41 of the sixth heat exchanger 3HE6 to the charging line 411 of the airstorage 303, and the sixth bypass conduit 407 includes a sixth bypassair flow control valve 408.

The present embodiment of the present invention also includes sevensupply conduits connected to the second circuits of the heat exchangers3HE1, 3HE2, 3HE3, 3HE4, 3HE5, 3HE6, 3HE7, and seven return conduitsconnected to the second circuits of the heat exchangers 3HE1, 3HE2,3HE3, 3HE4, 3HE5, 3HE6, 3HE7. The first supply conduit 450 connects thesupply manifold 347 to the inlet 13 of the second circuit 14 of thefirst heat exchanger 3HE1, and the first supply conduit 450 includes afirst fluid flow control valve 451.

The second supply conduit 452 connects the supply manifold 347 to theinlet 19 of the second circuit 20 of the second heat exchanger 3HE2, andthe second supply conduit 452 includes a second fluid flow control valve453.

The third supply conduit 454 connects the supply manifold 347 to theinlet 25 of the second circuit 26 of the third heat exchanger 3HE3, andthe third supply conduit 454 includes a third fluid flow control valve455.

The fourth supply conduit 456 connects the supply manifold 347 to theinlet 31 of the second circuit 32 of the fourth heat exchanger 3HE4, andthe fourth supply conduit 456 includes a fourth fluid flow control valve457.

The fifth supply conduit 458 connects the supply manifold 347 to theinlet 37 of the second circuit 38 of the fifth heat exchanger 3HE5, andthe fifth supply conduit 458 includes a fifth fluid flow control valve459.

The sixth supply conduit 460 connects the supply manifold 347 to theinlet 43 of the second circuit 44 of the sixth heat exchanger 3HE6, andthe sixth supply conduit 460 includes a sixth fluid flow control valve461.

The seventh supply conduit 462 connects the supply manifold 347 to theinlet 49 of the second circuit 50 of the seventh heat exchanger 3HE7,and the seventh supply conduit 462 includes a first fluid flow controlvalve 463.

As those skilled in the art will readily appreciate, the flow controlvalves 451, 453, 455, 457, 459, 461, 463 in the supply conduits 450,452, 454, 456, 458, 460, 462 are used as trim valves to increase ordecrease the flow rate of coolant or heat transfer fluid through thesecond circuit of the heat exchangers HE1, HE2, HE3, HE4, HE5, HE6, HE7to optimize the temperature and pressure of the compressed air enteringthe compressor stages and expander stages of the present embodiment.While this results in more efficient operation of the compressor stagesand expander stages, these flow control valves are optional 451, 453,455, 457, 459, 461, 463 and may be eliminated if such optimization isnot desired for a particular HOMC application.

The first return conduit 464 connects the return manifold 348 to theoutlet 15 of the second circuit 14 of the first heat exchanger 3HE1, andthe first return conduit 464 includes a first fluid flow control valve465.

The second return conduit 466 connects the return manifold 348 to theoutlet 21 of the second circuit 20 of the second heat exchanger 3HE2,and the second return conduit 466 includes a second fluid flow controlvalve 467.

The third return conduit 468 connects the return manifold 348 to theoutlet 27 of the second circuit 26 of the third heat exchanger 3HE3, andthe third return conduit 468 includes a third fluid flow control valve469.

The fourth return conduit 470 connects the supply manifold 348 to theoutlet 33 of the second circuit 32 of the fourth heat exchanger 3HE4,and the fourth supply conduit 470 includes a fourth fluid flow controlvalve 471.

The fifth return conduit 472 connects the return manifold 348 to theoutlet 39 of the second circuit 38 of the fifth heat exchanger 3HE5, andthe fifth return conduit 472 includes a fifth fluid flow control valve473.

The sixth return conduit 474 connects the return manifold 348 to theoutlet 45 of the second circuit 44 of the sixth heat exchanger 3HE6, andthe sixth return conduit 474 includes a sixth fluid flow control valve475.

The seventh return conduit 474 connects the return manifold 348 to theoutlet 51 of the second circuit 50 of the seventh heat exchanger 3HE7,and the seventh return conduit 474 includes a seventh fluid flow controlvalve 475.

The preferred embodiment of the present invention has two compressionmodes, one that is used when the air storage 303 is empty (the “CompleteAir Storage Compression Mode”) and another that may be used when the airstorage 303 has residual compressed air from being previously chargedwith compressed air (the “Partial Air Storage Compression Mode”).

In the Complete Air Storage Mode, prior to beginning the compressionoperation, all of the flow control valves are in the closed position.When the air compression is about to begin, the flow control valve 350in the coolant supply line 349, the flow control valve 351 in thecoolant return line 84, and the flow control valves 451, 453, 455, 457,459, 461, 463, 465, 467, 469, 471, 473, 475, 477 in the supply conduits450, 452, 454, 456, 458, 460, 462 and return conduits 464, 466, 468,470, 472, 474, 476 connected to the second circuits 14, 20, 26, 32, 38,44, 50 of the heat exchangers 3HE1, 3HE2, 3HE3, 3HE4, 3HE5, 3HE6, 3HE7,are opened, and the coolant circulating pump 311 is turned on. Oncecoolant from the cooling tower 315 is being circulated through thesecond circuit 14, 20, 26, 32, 38, 44, 50 of each of the heat exchangers3HE1, 3HE2, 3HE3, 3HE4, 3HE5, 3HE6, 3HE7 that has a compressor stage3C1, 3C2, 3C3, 3C4, 3C5, 3C6, 3C7 connected to the inlet of the firstcircuit thereof, the air flow control valve 322 in the first compressionconduit 321 is opened fully, and the air flow control valve 398 in thefirst bypass conduit 397 is opened partially. Then the flow controlvalve 64 in the third hydraulic line 63 is opened, the electric motor308 that drives the first compressor stage 3C1 is turned on, and thefirst compressor stage 3C1 begins drawing in ambient air and expellingthat air through the outlet 3C1O thereof. As those skilled in the artwill readily appreciate, centrifugal compressor stages need a certainbackpressure in order to compress air efficiently, and this backpressureis achieved by keeping the air flow control valve 398 in the firstbypass conduit 397 only partially opened while the air pressure thereinrises. Once the air pressure in the first bypass conduit 397 stopsrising and reaches a steady state pressure, the air flow control valve398 in the first bypass conduit 397 is regulated (i.e. opened in smallincrements) to allow the maximum air flow therethrough while maintainingthat steady state pressure. Under these conditions, air that iscompressed from ambient to the steady state pressure experiences asignificant increase in the temperature of the compressed air exitingthe first compressor stage 3C1. As that compressed air flows through thefirst heat exchanger 3HE1, it loses heat to the coolant flowing throughthe second circuit 14 thereof, cooling the compressed air and allowingthe first compressor stage 3C1 to operate more efficiently.

Since the flow control valve 64 in the third hydraulic line 63 is open,the pressure of the compressed air exiting the first compressor 3C1 andentering the air storage 303 drives the hydraulic fluid from the airstorage 303 and into the hydraulic tank 306. After substantially all ofthe hydraulic fluid has been driven from the air storage 303 by thecompressed air, the flow control valve 64 in the third hydraulic line 63is closed so that the air storage 303 is no longer in fluidcommunication with the hydraulic tank 306, causing the pressure of thecompressed air in the air storage 303 to rise.

The air flow control valve 398 in the first bypass conduit 397 continuesto be regulated until the compressed air in the air storage 303 hasachieved substantially the same pressure as the steady state pressure inthe first bypass conduit 397 upstream of the air flow control valve 398therein. Once this occurs, the second compressor stage 3C2 is turned on,if it is not already running, the air flow control valve 400 in thesecond bypass conduit 399 is opened partially, the air flow controlvalves 324, 326 in the second and third compression conduits 323, 325are opened fully, and the air flow control valve 398 in the first bypassconduit 397 is closed.

This causes the second compressor stage 3C2 to begin drawing incompressed air from the outlet 12 of the first circuit 11 of the firstheat exchanger 3HE1 and expelling compressed air through the outlet 3C2Oof the second compressor stage 3C2 and into the inlet 16 of the firstcircuit 17 of the second heat exchanger 3HE2, losing heat to the coolantflowing through the second circuit 20 thereof, cooling the compressedair. As the second compressor stage 3C2 continues to run, the airpressure in the second bypass conduit 399 rises. Once the air pressurein the second bypass conduit 399 stops rising and reaches a steady statepressure, the air flow control valve 400 in the second bypass conduit399 is regulated to allow the maximum air flow therethrough whilemaintaining that steady state pressure of the compressed air.

The air flow control valve 400 in the second bypass conduit 399continues to be regulated until the compressed air in the air storage303 has achieved substantially the same pressure as the steady statepressure in the second bypass conduit 399 upstream of the air flowcontrol valve 400 therein. Once this occurs, the third compressor stage3C3 is turned on, if it is not already running, the air flow controlvalve 402 in the third bypass conduit 401 is opened partially, the airflow control valves 328, 330 in the fourth and fifth compressionconduits 327, 329 are opened fully, and the air flow control valve 400in the second bypass conduit 399 is closed.

This causes the third compressor stage 3C3 to begin drawing incompressed air from the outlet 18 of the first circuit 17 of the secondheat exchanger 3HE2 and expelling compressed air through the outlet 3C3Oof the third compressor stage 3C3 and into the inlet 22 of the firstcircuit 23 of the third heat exchanger 3HE3, losing heat to the coolantflowing through the second circuit 26 thereof, cooling the compressedair. As the third compressor stage 3C3 continues to run, the airpressure in the third bypass conduit 401 rises. Once the air pressure inthe third bypass conduit 401 stops rising and reaches a steady statepressure, the air flow control valve 402 in the third bypass conduit 401is regulated to allow the maximum air flow therethrough whilemaintaining that steady state pressure of the compressed air.

The air flow control valve 402 in the third bypass conduit 401 continuesto be regulated until the compressed air in the air storage 303 hasachieved substantially the same pressure as the steady state pressure inthe third bypass conduit 401 upstream of the air flow control valve 402therein. Once this occurs, the fourth compressor stage 3C4 is turned on,if it is not already running, the air flow control valve 404 in thefourth bypass conduit 403 is opened partially, the air flow controlvalves 332, 334 in the sixth and seventh compression conduits 331, 333are opened fully, and the air flow control valve 402 in the third bypassconduit 401 is closed.

This causes the fourth compressor stage 3C4 to begin drawing incompressed air from the outlet 24 of the first circuit 23 of the thirdheat exchanger 3HE3 and expelling compressed air through the outlet 3C4Oof the fourth compressor stage 3C4 and into the inlet of the firstcircuit 28 of the fourth heat exchanger 3HE4, losing heat to the coolantflowing through the second circuit 32 thereof, cooling the compressedair. As the fourth compressor stage 3C4 continues to run, the airpressure in the fourth bypass conduit 403 rises. Once the air pressurein the fourth bypass conduit 403 stops rising and reaches a steady statepressure, the air flow control valve 404 in the fourth bypass conduit403 is regulated to allow the maximum air flow therethrough whilemaintaining that steady state pressure of the compressed air.

The air flow control valve 404 in the fourth bypass conduit 403continues to be regulated until the compressed air in the air storage303 has achieved substantially the same pressure as the steady statepressure in the fourth bypass conduit 403 upstream of the air flowcontrol valve 404 therein. Once this occurs, the fifth compressor stage3C5 is turned on, if it is not already running, the air flow controlvalve 406 in the fifth bypass conduit 405 is opened partially, the airflow control valves 336, 338 in the eighth and ninth compressionconduits 335, 337 are opened fully, and the air flow control valve 404in the fourth bypass conduit 403 is closed.

This causes the fifth compressor stage 3C5 to begin drawing incompressed air from the outlet 30 of the first circuit 29 of the fourthheat exchanger 3HE4 and expelling compressed air through the outlet 3C5Oof the fifth compressor stage 3C5 and into the inlet 34 of the firstcircuit 35 of the fifth heat exchanger 3HE5, losing heat to the coolantflowing through the second circuit 38 thereof, cooling the compressedair. As the fifth compressor stage 3C5 continues to run, the airpressure in the fifth bypass conduit 405 rises. Once the air pressure inthe fifth bypass conduit 405 stops rising and reaches a steady statepressure, the air flow control valve 406 in the fifth bypass conduit 405is regulated to allow the maximum air flow therethrough whilemaintaining that steady state pressure of the compressed air.

The air flow control valve 406 in the fifth bypass conduit 405 continuesto be regulated until the compressed air in the air storage 303 hasachieved substantially the same pressure as the steady state pressure inthe fifth bypass conduit 405 upstream of the air flow control valve 406therein. Once this occurs, the sixth compressor stage 3C6 is turned on,if it is not already running, the air flow control valve 408 in thesixth bypass conduit 407 is opened partially, the air flow controlvalves 340, 342 in the tenth and eleventh compression conduits 339, 341are opened fully, and the air flow control valve 406 in the fifth bypassconduit 405 is closed.

This causes the sixth compressor stage 3C6 to begin drawing incompressed air from the outlet 36 of the first circuit 35 of the fifthheat exchanger 3HE5 and expelling compressed air through the outlet 3C6Oof the sixth compressor stage 3C6 and into the inlet 40 of the firstcircuit 41 of the sixth heat exchanger 3HE6, losing heat to the coolantflowing through the second circuit 44 thereof, cooling the compressedair. As the sixth compressor stage 3C6 continues to run, the airpressure in the sixth bypass conduit 407 rises. Once the air pressure inthe sixth bypass conduit 407 stops rising and reaches a steady statepressure, the air flow control valve 408 in the sixth bypass conduit 407is regulated to allow the maximum air flow therethrough whilemaintaining that steady state pressure of the compressed air.

The air flow control valve 408 in the sixth bypass conduit 407 continuesuntil the compressed air in the air storage 303 has achievedsubstantially the same pressure as the steady state pressure in thesixth bypass conduit 407 upstream of the air flow control valve 408therein. Once this occurs, the seventh compressor stage 3C7 is turnedon, if it is not already running, the air flow control valve 410 in thefourteenth compression conduit 409 is opened partially, the air flowcontrol valves 344, 346 in the twelfth and thirteenth compressionconduits 343, 345 are opened fully, and the air flow control valve 408in the sixth bypass conduit 407 is closed.

This causes the seventh compressor stage 3C7 to begin drawing incompressed air from the outlet 42 of the first circuit 41 of the sixthheat exchanger 3HE6 and expelling compressed air through the outlet 3C7Oof the seventh compressor stage 3C7 and into the inlet 46 of the firstcircuit 47 of the seventh heat exchanger 3HE7, losing heat to thecoolant flowing through the second circuit 50 thereof, cooling thecompressed air. As the seventh compressor stage 3C7 continues to run,the air pressure in the fourteenth compression conduit 409 rises. Oncethe air pressure in the fourteenth compression conduit 409 stops risingand reaches a steady state pressure, the air flow control valve 410 inthe fourteenth conduit 409 is regulated to allow the maximum air flowtherethrough while maintaining that steady state pressure of thecompressed air in the fourteenth conduit 409 upstream of the air flowcontrol valve 410 therein. The compressor stages continue to run in thismanner until the air storage 303 has reached the desired pressure, atwhich point all of the flow control valves are closed and the motors308, 311 driving the compressor stages 3C1, 3C2, 3C3, 3C4, 3C5, 3C6, 3C7and circulating pump 311 are shut off.

As those skilled in the art will readily appreciate, if the type ofcompressors used incorporate variable compressor guide vanes, such vanesmay be able to perform some of the flow control functions describedherein such as providing backpressure to the compressors and restrictingair flow to certain compressors during process of storing compressed airin the air storage 303.

Operation in the Partial Air Storage Compression Mode is similar to thatdescribed above for the Complete Air Storage Compression Mode, exceptthat once the compressed air in the first bypass conduit 397 upstream ofthe air flow control valve 398 reaches a steady state condition, if thepressure of the compressed air in the air storage is higher than thecompressed air in the first bypass conduit 397 upstream of the air flowcontrol valve 398, that air flow control valve 398 is fully closed andthe air flow control valves 324, 326 in the second and third conduits323, 325 open to allow the compressed air flowing from the outlet 12 ofthe first circuit 11 of the first heat exchanger 3HE1 to flow throughthe second compressor stage 3C2, through the first circuit 17 in thesecond heat exchanger 3HE2, and into the second bypass conduit 399. Oncethe compressed air in the second bypass conduit 399 upstream of the airflow control valve 400 reaches a steady state condition, if the pressureof the compressed air in the air storage 303 is still higher than thecompressed air in the second bypass conduit 399 upstream of the air flowcontrol valve 400, that air flow control valve 400 is fully closed andthe air flow control valves 328, 330 in the fourth and fifth conduits327, 329 open to allow the compressed air flowing from the outlet 18 ofthe first circuit 17 of the second heat exchanger 3HE2 to flow throughthe third compressor stage 3C3, through the first circuit 23 in thethird heat exchanger 3HE3, and into the third bypass conduit 401. Thisprocess continues through the remaining compressor stages 3C4, 3C5, 3C6,3C7 until a condition is reached where the steady state pressureachieved in one of the bypass conduits exceeds the pressure of thecompressed air in the air storage 303. Once that condition is met, thecompression process continues from that point forward as described abovefor the Complete Air Storage Compression Mode.

When it is desired to generate electricity from the compressed air inthe air storage, the manner in which the compressed air is releaseddepends on whether all of the energy in the compressed air is to be usedfor power generation (the “Sliding Pressure Mode”), or whether themaximum and/or minimum pressure of the compressed air delivered to thefirst expander stage E1 is to be regulated (the “Regulated PressureMode”), which is discussed in greater detail below.

In the Sliding Pressure Mode, prior to beginning the expansionoperation, all of the flow control valves are in the closed position,and the gas turbine exhaust is heating the heat exchanger 318 in the gasturbine exhaust case. When expansion of the compressed air is about tobegin, the flow control valve 353 in the heat transfer fluid supply line352, the flow control valve 355 in the heat transfer fluid return line354, and the flow control valves 451, 453, 455, 457, 459, 461, 463, 465,467, 469, 471, 473, 475, 477 in the supply conduits 450, 452, 454, 456,458, 460, 462 and return conduits 464, 466, 468, 470, 472, 474, 476connected to the second circuits 14, 20, 26, 32, 38, 44, 50 of the heatexchangers 3HE1, 3HE2, 3HE3, 3HE4, 3HE5, 3HE6, 3HE7, are opened and theheat transfer fluid circulating pump 312 is turned on. Then the flowcontrol valve 361 in the compressed air supply line 317 is opened, theflow control valves 376, 378, 380, 382, 384, 386, 388, 390, 392, 394,396 in each of the expansion conduits 375, 377, 379, 381, 383, 385, 387,389, 391, 393, 395 are opened, and the flow control valve 364 in thefirst compressed air manifold discharge conduit 363 is opened. Thisallows compressed air to flow from the air storage 303 through thecompressed air supply line 317, through the first circuit 76 of thepre-heater heat exchanger 319, into the compressed air manifold 314, outthe first outlet 82 thereof, and into the first compressed air manifolddischarge conduit 363. Compressed air from the first compressed airmanifold discharge conduit 363 flows into the inlet 40 of the firstcircuit 41 of the sixth heat exchanger 3HE6, through the first circuitthereof 41, and out the outlet 42 of the first circuit 41, being heatedby the hot heat transfer fluid circulating through the second circuit 44thereof to approximately the same temperature as the heat transferfluid.

The heated, compressed air exiting the sixth heat exchanger 3HE6 thenflows through the first expansion conduit 375 to the inlet 3E1I of thefirst expander stage 3E1, expands through the first expander stage 3E1performing work that drives the generator 304, and then exits the firstexpander stage 3E1 into the second expansion conduit 377 at asubstantially lower pressure and temperature. This cooler compressed airthen flows from the second expansion conduit 377 into the inlet 34 ofthe first circuit 35 of the fifth heat exchanger 3HE5, through the firstcircuit 35 thereof, and out the outlet of the first circuit 35, beingheated by the heat transfer fluid circulating through the second circuit38 thereof back up to approximately the same temperature as the heattransfer fluid.

The heated, compressed air exiting the fifth heat exchanger 3HE5 thenflows through the third expansion conduit 379 to the inlet 3E2I of thesecond expander stage 3E2, expands through the second expander stage 3E2performing work that drives the generator 304, and then exits the secondexpander stage 3E2 into the fourth expansion conduit 381 at asubstantially lower pressure and temperature. This cooler compressed airthen flows from the fourth expansion conduit 381 into the inlet 28 ofthe first circuit 29 of the fourth heat exchanger 3HE4, through thefirst circuit 29 thereof, and out the outlet 30 of the first circuit 29,being heated by the heat transfer fluid circulating through the secondcircuit 32 thereof back up to approximately the same temperature as theheat transfer fluid.

The heated, compressed air exiting the fourth heat exchanger 3HE4 thenflows through the fifth expansion conduit 383 to the inlet 3E3I of thethird expander stage 3E3, expands through the third expander stage 3E3performing work that drives the generator 304, and then exits the thirdexpander stage 3E3 into the sixth expansion conduit 385 at asubstantially lower pressure and temperature. This cooler compressed airthen flows from the sixth expansion conduit 385 into the inlet 22 of thefirst circuit 23 of the third heat exchanger 3HE3, through the firstcircuit 23 thereof, and out the outlet 24 of the first circuit 23, beingheated by the heat transfer fluid circulating through the second circuit26 thereof back up to approximately the same temperature as the heattransfer fluid.

The heated, compressed air exiting the third heat exchanger 3HE3 thenflows through the seventh expansion conduit 387 to the inlet 3E4I of thefourth expander stage 3E4, expands through the fourth expander stage 3E4performing work that drives the generator 304, and then exits the fourthexpander stage 3E4 into the eighth expansion conduit 389 at asubstantially lower pressure and temperature. This cooler compressed airthen flows from the eighth expansion conduit 389 into the inlet 16 ofthe first circuit 17 of the second heat exchanger 3HE2, through thefirst circuit 17 thereof, and out the outlet 18 of the first circuit 17,being heated by the heat transfer fluid circulating through the secondcircuit thereof back up to approximately the same temperature as theheat transfer fluid.

The heated, compressed air exiting the second heat exchanger 3HE2 thenflows through the ninth expansion conduit 391 to the inlet 3E5I of thefifth expander stage 3E5, expands through the fifth expander stage 3E5performing work that drives the generator 304, and then exits the fifthexpander stage 3E5 into the tenth expansion conduit 393 at asubstantially lower pressure and temperature. This cooler compressed airthen flows from the tenth expansion conduit 393 into the inlet 10 of thefirst circuit 11 of the first heat exchanger 3HE1, through the firstcircuit 11 thereof, and out the outlet 12 of the first circuit 11, beingheated by the heat transfer fluid circulating through the second circuitthereof back up to approximately the same temperature as the heattransfer fluid.

The heated, compressed air exiting the first heat exchanger 3HE1 thenflows through the eleventh expansion conduit 395 to the inlet 3E6I ofthe sixth expander stage 3E6, expands through the sixth expander stage3E6 performing work that drives the generator 304, and then exits thesixth expander stage 3E6 into the second circuit 75 of the pre-heaterheat exchanger 319, thereby heating the compressed air flowing from thecompressed air supply line 317 through the first circuit 76 of thepre-heater heat exchanger 319, and on to the compressed air manifold314. The compressed air from the sixth expander stage 3E6 then exits thesecond circuit 75 of the pre-heater heat exchanger 319 and is exhaustedinto the atmosphere.

As those skilled in the art will readily appreciate, as the expanderstages 3E1, 3E2, 3E3, 3E4, 3E5, 3E6 are running, the pressure of thecompressed air in the air storage 303 is decreasing, and at some pointthe pressure of the compressed air remaining in the air storage 303 willbe insufficient to drive all of the expander stages 3E1, 3E2, 3E3, 3E4,3E5, 3E6, with the result that some of the downstream expander stageswill not be able to drive the generator 304, and may themselves becomemerely a load on the generator 304. To avoid this, in the SlidingPressure Mode of operation of the present invention, when the pressureof the compressed air in the air storage 30 falls to a predeterminedpressure, the air flow control valve 366 in the second compressed airmanifold discharge conduit 365 is opened and the air flow control valve364 in the first compressed air manifold discharge conduit 363, and theflow control valves 376, 378 in the first and second expansion conduits375, 377, are closed. Doing so bypasses the first expander stage 3E1,redirecting the compressed air from the air storage 303 to the fifthheat exchanger 3HE5 and the second expander stage 3E2, thereby allowingthe remaining expander stages 3E2-3E6 to continue generating electricalpower as described above, although not as much electrical power as wasbeing generated just prior to the first expander stage 3E1 beingbypassed.

The expander stages 3E2, 3E3, 3E4, 3E5, 3E6 that have not been bypassedcontinue to operate as described above until the pressure of thecompressed air in the air storage 303 falls to a second predeterminedpressure, at which point the air flow control valve 368 in the thirdcompressed air manifold discharge conduit 367 is opened and the air flowcontrol valve 366 in the second compressed air manifold dischargeconduit 365, and the flow control valves 380, 382 in the third andfourth expansion conduits 379, 381 are closed. Doing so bypasses thesecond expander stage 3E2, redirecting the compressed air from the airstorage 303 to the fourth heat exchanger 3HE4 and the third expanderstage 3E3, thereby allowing the remaining expander stages 3E3-3E6 tocontinue generating electrical power as described above, although not asmuch electrical power as was being generated just prior to the secondexpander stage 3E2 being bypassed.

This process continues as the pressure of the compressed air in the airstorage 303 falls to a third, fourth and fifth predetermined pressure,and as the pressure of the compressed air in the air storage 303 reacheseach predetermined pressure, the expander stage receiving the highestpressure compressed air is bypassed by closing the air flow controlvalves in the expansion conduits connected thereto, and opening the airflow control valve in the compressed air manifold discharge conduit thatis connected to the inlet of the same heat exchanger that the expansionconduit connected to the outlet of such expander stage is connected. Theexpander stages that have not been bypassed continue to operate asdescribed above until the pressure of the compressed air in the airstorage 303 is too low to drive just the sixth expander stage 3E6, atwhich point compressed air electrical generation stops, and all of theflow control valves are closed.

As those skilled in the art will readily appreciate, the SlidingPressure Mode allows the efficient use of all of the compressed air inthe air storage for the generation of electricity, but the megawattoutput using the Sliding Pressure Mode is constantly decreasing. Forsome power plant operators, it may be desirable sacrifice someefficiency by throttling the compressed air exiting the airstorage—which inherently introduces inefficiencies as a pressure drop istaken across the throttle without useful work being performed—in orderto produce a constant level of megawatts over a fixed period of time,such as when an electrical grid operator requests a power plant operatorto increase power production by 10 MW for four hours. In this situation,the plant operator may want to operate the present embodiment of thepresent invention in the Regulated Pressure Mode. For example, if thepressure of the compressed air in the air storage is 1200 psi, but theexpansion circuit only needs the compressed air entering the firstexpander stage 3E1 to be 800 psi for the expansion circuit to generate10 MW, then a regulator 305, such as that shown in FIGS. 3A and 3B inthe compressed air supply line 317 leading from the air storage 303, canbe used to throttle the compressed air exiting the air storage 303 downto 800 psi throughout the period of electrical generation. In this mode,the expansion circuit starts in the same manner as described above forthe Sliding Pressure Mode, but it never reaches the point where thefirst expander stage 3E1 gets bypassed, because the electrical powergeneration is manually stopped before the pressure of the compressed airin the air storage 303 falls to the predetermined pressure that wouldtrigger the bypassing of the first expander stage 3E1 as describedabove.

In order to avoid the inefficiencies associated with throttling asdiscussed above, while maintaining the compressed air entering thepre-heater heat exchanger 319 at a predetermined constant pressure, ahydraulic fluid, such as water, can be pumped from a water tank 306, asshown in FIGS. 3A and 3B, into the air storage at the predeterminedpressure and at a rate sufficient to prevent a drop in the pressure ofthe compressed air in the air storage 303 as the compressed air is fedto the expander stages 3E1, 3E2, 3E3, 3E4, 3E5, 3E6. For example, if itis desired to maintain the pressure of the compressed air in the airstorage 303 at 800 psi, a water pump 307 capable of pumping water at 800psi and at a rate sufficient to maintain the compressed air at 800 psican be used. Since the energy required to run such a water pump 307 isless than the energy that can be produced by heating the compressed airas it is expanded through the expander stages 3E1, 3E2, 3E3, 3E4, 3E5,3E6 of the present invention, the full energy benefit of the compressedair in the air storage 303 can be obtained while still producingadditional electricity from the generator without resorting to theSliding Pressure Mode.

Using the secondary heat to heat the compressed air up to apredetermined temperature, which may be nearly as high as the exhaustgas temperature of the gas turbine 301 supplying the secondary heat(depending upon losses that occur in transferring heat from the exhaustgas and to the compressed air) prior to such compressed air enteringeach expander stage 3E1, 3E2, 3E3, 3E4, 3E5, 3E6 results in the abilityto generate more electric power from the same mass of compressed air inthe air storage 303 than if the compressed air were not heated prior toentering each of the expander stages 3E1, 3E2, 3E3, 3E4, 3E5, 3E6. Thisalso means that by using such inter-stage heating as described in thepresent invention, a smaller volume of air storage 303 and/or fewer airstorage tanks could provide the same electrical power generation as asimilar system in which the compressed air is heated up to the sametemperature before the first expander stage, but not before anysubsequent expander stages. Likewise, pumping water into the air storage303 with a high pressure pump 307 to maintain the pressure in the airstorage 303 at a pre-determined pressure until all of the compressed airhas been driven out of the air storage 303 results in the ability togenerate more electric power from the same mass of compressed air in theair storage 303 than can be can be generated by allowing the air storage303 to “bleed down”, as in the case of the Sliding Pressure Mode. Thisalso means that by introducing high pressure water into the air storage303 as described in the present invention, a smaller volume of, and/orfewer, air storage tanks could provide the same electrical powergeneration as a similar system in which the compressed air pressuresimply bleeds down to ambient as the expander stages 3E1, 3E2, 3E3, 3E4,3E5, 3E6 extract work from the compressed air.

In fact, by using secondary heat to heat the compressed air up to apredetermined temperature prior to such compressed air entering eachexpander stage 3E1, 3E2, 3E3, 3E4, 3E5, 3E6, as described above, and bypumping water into the air storage 303 with a high pressure pump 307 tomaintain the pressure in the air storage 303 at a pre-determinedpressure, as described above, the present embodiment of the presentinvention can produce the same megawatt hours of electrical power withone-fifth of the air storage volume that would be required to producethat amount of electrical power if no secondary heat were used to heatthe compressed air up to a predetermined temperature prior to suchcompressed air entering each expander stage, and if no pumping of waterinto the air storage 303 with a high pressure pump 307 were done tomaintain the pressure of the compressed air in the air storage 303 at apre-determined pressure. Since the cost of the air storage 303represents more than half of the cost of a typical CAES system for thoseinstallations where neither a cavern, nor other suitable geologicstorage such as porous media, is available to provide air storage 303,this reduction represents a substantial reduction in the initial cost ofimplementing HOMC at an existing gas turbine site.

Those skilled in the art will also appreciate that the presentembodiment of the present invention is also capable of being operated inhybrid modes, such as starting and operating the expansion circuit asdescribed for the Sliding Pressure Mode, but then closing the air flowcontrol valve in the compressed air supply line leading from the airstorage when the pressure of the compressed air in the air storagereaches a predetermined minimum pressure. Likewise, the presentembodiment of the present invention is capable of starting and operatingthe expansion circuit as described for the Regulated Pressure Mode, butthen shifting to the Sliding Pressure Mode when the pressure of thecompressed air in the air storage reaches a predetermined minimumpressure.

A first alternate embodiment of the present is shown in FIGS. 4A and 4Bwhich is similar to the preferred embodiment, except that rather thantransferring heat from the exhaust of a gas turbine 301 to the heattransfer fluid (hot water) using an air to liquid heat exchanger mountedin the gas turbine exhaust case, the exhaust gas from the gas turbine301 is ducted 501 over to the location of the HOMC, where it goesthrough an exhaust-gas-to-water heat exchanger 318 and is then returnedto the gas turbine exhaust through a return duct 502. Optionally, toeliminate the need for an exhaust system on the HOMC system at all, theexpander exhaust 320 can be added to the return duct 502. The heattransfer fluid, or hot water, from the gas turbine exhaust heatexchanger 318 is then used to heat the compressed air entering theexpander stages 3E1, 3E2, 3E3, 3E4, 3E5, 3E6 in the same manner asdescribed previously with respect to the preferred embodiment. Thisfirst alternate embodiment eliminates the need for the addition of highpressure piping to the plant operators site, while also minimizing theeffect on the plant operator's existing gas turbine 301. In all otherrespects, the first alternate embodiment of the present inventionoperates in the same manner as described above for the preferredembodiment. Accordingly, the first alternate embodiment of the presentinvention can be operated in the Sliding Pressure Mode, the RegulatedPressure Mode, and the hybrid modes discussed above.

A second alternate embodiment of the present invention is shown in FIGS.5A and 5B which is similar to the first alternate embodiment, exceptthat in this embodiment 1) the gas turbine exhaust is ducted to anexhaust-gas-to-air heat exchanger instead of an exhaust-gas-to-waterheat exchanger, 2) the expansion circuit is decoupled from the heatexchangers 3HE1, 3HE2, 3HE3, 3HE4, 3HE5, 3HE6, 3HE7 used in thecompression circuit such that the compression circuit has its ownmanifolds 347, 348 and heat exchangers 3HE1, 3HE2, 3HE3, 3HE4, 3HE5,3HE6, 3HE7, and the expansion circuit has its own manifolds 550, 551 andsix air-to-air heat exchangers 5HE8, 5HE9, 5HE10, 5HE11, 5HE12, 5HE13,and one pre-heater heat exchanger 319. Since the heat exchangers used inthe compression circuit use a liquid coolant, they cannot double as heatexchangers for the expansion circuit due to the differences in the heattransfer medium used. Accordingly, a separate bank of air-to-air heatexchangers (5HE8, 5HE9, 5HE10, 5HE11, 5HE12, 5HE13) is used exclusivelywith the expander stages (3E1, 3E2, 3E3, 3E4, 3E5, 3E6). Such a systemmay be desirable if a power plant needs to generate additional megawattsof power (“Power Augmentation Mode”) for a sustained period of time(i.e. days rather than hours) as described in greater detail below. Asthose skilled in the art will readily appreciate, the Power AugmentationMode can also be used with the preferred embodiment and the firstalternate embodiment if separate heat exchangers are provided for thecompressor circuit and the expander circuit in the manner shown for thesecond alternate embodiment.

The compression circuit of the second alternate embodiment of thepresent invention is the same as described for the preferred embodiment,and, except for the changes described with respect to the heating of thehot water described in the first alternate embodiment, the heat transferfluid supply circuit is also the same. Likewise, the expansion circuitof the second alternate embodiment of the present invention is similarto that described for the preferred embodiment, but in the secondalternate embodiment of the present invention, the eighth heat exchanger3HE8 replaces the sixth heat exchanger 3HE6, the ninth heat exchanger3HE9 replaces the fifth heat exchanger 3HE5, the tenth heat exchanger5HE10 replaces the fourth heat exchanger 3HE4, the eleventh heatexchanger 5HE11 replaces the third heat exchanger 3HE3, the twelfth heatexchanger 5HE12 replaces the second heat exchanger 3HE2, and thethirteenth heat exchanger 5HE13 replaces the first heat exchanger 3HE1.Other than the replacement of the foregoing heat exchangers in theoperation of the expansion circuit, the expansion operation is similarto that described for the preferred embodiment of the present invention.Accordingly, the second alternate embodiment of the present inventioncan be operated in the Sliding Pressure Mode, the Regulated PressureMode, and the hybrid modes discussed above. In addition, because thesecond embodiment of the present invention has heat exchangers 5HE8,5HE9, 5HE10, 5HE11, 5HE12, 5HE13 that are dedicated to the expansionoperation, the compression operation and the expansion operation canoperate simultaneously in the Power Augmentation Mode as describedbelow, unlike the systems used in the preferred embodiment and the firstalternate embodiment of the present invention.

Since these embodiments use secondary heat from a heat source, such asan existing gas turbine, that would otherwise be released to theatmosphere, these embodiments output more megawatts of energy than theyconsume. For example, if there is sufficient exhaust gas available fromthe gas turbine 301, or another source secondary heat, the compressedair flowing through heat exchangers 5HE8, 5HE9, 5HE10, 5HE11, 5HE12,5HE13 to a temperature of 850° F., the efficiency of the secondalternate embodiment of the present invention is 1.4 (where the energyin the secondary heat is not included as energy input in the calculationof efficiency). If there is sufficient exhaust gas available from thegas turbine to heat the compressed air flowing through heat exchangers5HE8, 5HE9, 5HE10, 5HE11, 5HE12, 5HE13 to a temperature of least 1050°F., the efficiency of this embodiment is 1.65, using the same formulafor efficiency calculation.

As those skilled in the art will readily appreciate, as long as theefficiency is greater than 1.0, the second alternate embodiment of thepresent invention can be used for power augmentation (“PowerAugmentation Mode”) by operating both the compression operation and theexpansion operation simultaneously, because the expansion operation,using secondary heat, produces more power than the compression operationand parasitic equipment consumes. For example, if the second alternateembodiment of the present invention is added to an existing GeneralElectric 7FA (“GE 7FA”) simple cycle gas turbine that is being used as a“peaker” (i.e. used when demand for electrical power peaks above thatlevel that can be supplied by base-load generation), it will provide allof the benefits associated with an energy storage system with anefficiency of 1.65. In addition, if it is desired to operate the presentinvention in a sustained Power Augmentation Mode, since both thecompressor stages 3C1, 3C2, 3C3, 3C4, 3C5, 3C6, 3C7 and the expanderstages 3E1, 3E2, 3E3, 3E4, 3E5, 3E6 can be run on a common shaft, withclutches, through the motor/generator 304, 308 such that a portion ofthe torque generated by the expander stages 3E1, 3E2, 3E3, 3E4, 3E5, 3E6is used to drive the compressor stages 3C1, 3C2, 3C3, 3C4, 3C5, 3C6, 3C7and the remainder is used to drive the generator 304 such that thecompressor stages charge the air storage 303 at the same rate theexpander stages consume compressed air from the air storage 303(provided that the pressure of the compressed air in the air storage isat least 800 psi), and since the efficiency of this embodiment is 1.65,the present invention will produce 1.65 MW for each 1 MW of energy itconsumes.

For example, since a GE 7FA produces approximately 1000 lb/sec exhaustflow, and a 10.3 MW version of the present embodiment needs 180 lbs/secto produce its rated power, approximately 57 MW of energy storage powercan be generated for 4 hours (if the air storage 303 is full and at apressure of 1200 psi) from the secondary heat of a GE 7FA, and when theair storage 303 reaches 800 psi, the HOMC can be operated in a PowerAugmentation Mode, where the expander stages, less the energy requiredto drive the compressors, generate a net output of 4.2 MW while runningsimultaneously, and 22 MW can be generated indefinitely, without usingany of the compressed air in the air storage 303, as long as the gasturbine 301 is running and producing exhaust gas. Therefore, while a GE7FA itself produces 194 MW, an additional 57 MW can be produced byexpansion of the compressed air through the expander stages as long asthe pressure of the compressed air in the air storage 303 is above 800psi. Once the pressure of the compressed air in the air storage 303falls to 800 psi, the compressor stages can be run to deliver compressedair at an 800 psi discharge pressure, (not 1200 psi because thecompressed air is going to be expanded as fast as it is compressed), andthe power consumed by the compression operation is reduced because thelast compression stage, the stage that normally compresses 800 psi airup to 1200 psi, is not engaged because there is no need to compress theair in the air storage 303 above 800 psi. The second alternateembodiment of the present invention in the Power Augmentation Mode on aGE 7FA can produce a net 22 MW of additional power for period of timethat is not limited by the volume of the air storage 303, if desired,representing an 11% increase in net power from the power plant, or a 11%reduction in heat rate.

As a means of illustrating the advantages of the HOMC cycle disclosedherein, a comparison of the relative energy output and the “round trip”efficiency obtained from the CAES2 and HOMC cycle is shown belowgiven 1) the same initial conditions (air storage, having a volume equalto 75,848 ft³ is full of compressed air) and 2) access to the sametemperature exhaust (1050° F. in the case of CAES2 and HOMC).

The volume of the air storage tank in this example was calculated bytaking the change in the mass of compressed air that must exit the airstorage to produce 4 hours of 10 MW output (as discussed below) dividedby the change in density of the compressed air remaining in the airstorage tank. The change in mass exiting the air storage tank is thedensity of the compressed air at 1200 psi (from standard thermodynamictables, at 80° F.) minus the density of the air in the tank at 14.7 psi(from standard thermodynamic tables, at 80° F.) which equals a densitychange of 5.81 lb/ft³. The change in mass of the compressed air exitingthe air storage tank is the mass flow (32 lb/sec, which produces 10 MWas shown below) multiplied by the output time of 4 hours (14,400seconds), or 460,800 lbs of air. Dividing this change in mass (460,800lbs) by the density change (5.81 lb/ft³) yields an air storage volume of79,292 ft³ to produce 10 MW for 4 hours. (This calculated air storagevolume was further reduced to 75,848 ft³ as described below.) With thechange in mass of compressed air being known (which is also function ofthe air storage volume), one can calculate how long it would take forcompressor flowing 28 lbs/sec to fill the air storage by dividing thechange in the mass of compressed air (460,800 lbs) by the flow rate (28lbs/sec), or 16,457 seconds (i.e. 4.57 hours). Therefore, it would take4.57 hours to fill an air storage having a volume of 79,292 ft³ from14.7 psi to 1200 psi. The compressor pump power and energy is calculatedas shown in Table 1 below:

TABLE 1 Compressor Power Flow = 32 lbm/s Compressor WITH Intercooling(GIVEN - 80° F. Coolant) P In P Out P T In T Out h In h Out Δh Power InPower In Stage [psia] [psia] Ratio [° F.] [° F.] [Btu/lbm] [Btu/lbm][Btu/lbm] Btu/s MW 1 14.7 33 2.22 90 244 131 169 37 1038 1.10 2 32.7 531.63 100 197 134 157 23 647 0.68 3 53.3 130 2.44 100 284 134 178 44 12351.30 4 130.0 273 2.10 100 257 134 172 38 1059 1.12 5 273.0 514 1.88 100323 134 188 54 1507 1.59 6 514.4 816 1.59 100 189 134 155 21 600 0.63 7800.0 1200 1.47 100 172 134 151 17 478 0.50 To Air 90 Σ 6564 6.92Storage

Assuming that the compression process for the SmartCAES, CAES2 and HOMCcycles is equivalent, (i.e. that they all use similar typeturbo-compressors with intercooling), the charging power required byeach stage, assuming isotropic compression, (which is a reasonableapproximation where intercooled compressor stages are used), thecompressor power is the change in enthalpy per stage of compressionwhich is driven by the temperature rise, which is related to thepressure ratio by the equation (TOut/Tin)=(Pout/Pin)(k−1)/k, where k is1.4, the gas constant for air. Using the first stage as an example,TOut=Tin*(Pout/Pin)(k−1)/k, where Tin=311° K (90° F.), Pout=33 psia, andPin=14.7 psia, Tout=311*(33/14.7)(1.4−1)/1.4)=394° K or (244° F.). Theoutlet temperature of each of the other compressor stages in Table 1 iscalculated the same way, and the pressure ratio is a given value drivenby the manufacturer of the air compressor's aerodynamics. For the typeof compressors in this example, each stage has a pressure ratio of ˜2.0.The total pump power any time the pressure in the tank is at 800 psi orabove is 6.92 MW.

To charge a 79,292 ft³ tank full with 1200 psi air as described withrespect to the present embodiments, only the first stage initiallycompresses air, using 1.1 MW, until the compressed air in the airstorage reaches 33 psi, at which time the exit flow of the first stagecompressor is redirected from the air storage to the inlet of the secondcompressor stage. The load for the second compressor stage is 0.68 MW,for a total compression load of 1.78 MW through the first two stages.This process continues as the compressed air in the air storage reachesthe output pressure of the current compressor stage until finally, thecompressed air in the air storage is at 815.6 psi, at which point theflow coming out of the 6th compressor stage is redirected from the airstorage to the inlet of the 7th, and final, compressor stage. At thispoint, the power required to run all seven compressor stages is 6.92 MW.In this example, throughout the time any of the compressor stages isrunning, the mass flow to the air storage is constant at 28 lbs/sec,while the pressure is increasing. Typically, these types of compressorstages are run in applications having constant inlet and exit pressures,where there is no need to modulate the compressed air from one stage toanother. Since the use of these compressor stages in the presentembodiment is not a typical run profile for these types of compressorstages, there is a need to modulate the compressed air from onecompressor stage to another as described above. Also, inlet guide vanesand exit guide vanes may be incorporated into the present embodiment sothat as the pressure within each stage is changing, the efficiency ofthe compressor stage can be maximized.

To calculate the total energy consumed while pumping the tank from 14.7psia to 1200 psia, an integration process is used which sums the energyused by all of the compressor stages. Each stage's charging time iscalculated by a process similar to that described above for the firstcompressor stage, where the change in density for any given stage ismultiplied by the total volume of the air storage and then divided bythe compressor mass flow rate of 28 lb/sec. Then, each compressorstage's energy consumption is simply that compressor stage's powerconsumption multiplied by the charging time for that particularcompressor stage. Since the power level for charging the tank from 32.2psi to 53.3 psi in the example below, is the sum of the first and secondpower level, or 1.78, the energy required to charge the air storage from32.2 psi to 53.3 psi is 1.78 MW multiplied by the time, 0.08 hrs, or 0.1MWh. Using this technique for all of the compressor stages and summing,the total energy required to charge the tank from tank from 14.7 psi to1200 psi is calculated to be 26.6 MWh, as shown in Table 2 below:

TABLE 2 Integration Process Summing Compressor Power 28 lb/s CompressorFlow Pressure 1 Pressure 2 Power Time Energy Stage Psia psia MW hrsMW-hr 1 14.7 32.7 1.1 0.07 0.1 2 32.7 53.3 1.78 0.08 0.1 3 53.3 130 3.080.30 0.9 4 130 273 4.2 0.55 2.3 5 273 514.4 5.79 0.93 5.4 6 514.4 815.66.42 1.16 7.5 7 815.6 1200 6.92 1.48 10.3 Σ 4.57 26.6

The expansion cycle is assumed to have 84% isentropic efficiency. Withthis assumption, and using the same rationale explained in thecompressor stages power calculation, an energy output through all of theexpander stages, with inter-stage reheat, yields an output of 11.3 MW,as shown in Table 3 below:

TABLE 3 800 psi Operating Expander WITH Interheating - 1050° F. ExhaustFlow = 32 lbm/s Isentropic T In T Out P In P Out P h In h Out Δh PowerOut Power Out Stage [° F.] [° F.] [pisa] [psia] Ratio [Btu/lbm][Btu/lbm] [Btu/lbm] Btu/s MW 1 1011 830 816 514 0.63 362 314 47 15161.60 2 1028 782 514 273 0.53 366 302 64 2050 2.16 3 1023 740 273 1300.48 365 291 74 2356 2.49 4 1019 687 130 53 0.41 363 278 86 2743 2.89 51014 822 53 33 0.61 362 312 50 1599 1.69 6 1027 724 33 15 0.45 366 28779 2520 2.66 AVG 724 Σ 12785 13.49 84% Efficient Power Out MW 11.3

The time required to deplete the pressure of the compressed air in thisair storage from 1200 psi to 800 psi during the expansion cycle is afunction of the change in density of the compressed air at those twopressures at 80° F., which from standard thermodynamic tables equals1.88 lb/ft³. Multiplying this change in density (1.88 lb/ft³ by the airstorage volume, 79,292 ft³, gives the change in mass of the compressedair in the air storage, or 149,440 lbs. Dividing this change in mass bythe expander flow rate of 32 lbs/s yields the time it takes to depletethe pressure of the compressed air in the air storage from 1200 psi to800 psi, that being 4,670 seconds, or 1.3 hours. In other words, theexpander cycle can run for 1.3 hours with an output of 11.3 MW beforethe pressure of the compressed air in the air storage falls to 800 psi.At this point the hydraulic pump is engaged to pump a hydraulic fluid,preferably water, to drive out the remainder of the compressed air inthe air storage (311,360 lbs) for an additional 2.7 additional hourswith a the net power output from the expander cycle of 10 MW. The pumppower required to fill the 79,292 ft³ tank with 800 psi hydraulic fluidwas determined from pump manufacturer specifications and a fill time of2.7 hours (balance of time left to deliver power for 4 hours, 2.7=4−1.3)which yields a pump flow rate of 3516 gpm at 800 psi and atmosphericinlet head and a pump power of 1.3 MW. The optimum output is a constantoutput (10 MW) for 4 hours, so for the first 1.3 hours, the expander canactually operated at a 12% lower flow rate and produce 10 MW, whichactually reduces the required volume of the air storage to 75,848 ft³and the required input energy to 25.4 MW. With a power output of 10 MWfor 4 hours, or an energy output of 40 MWh for the HOMC system, theround trip efficiency is 1.57 (i.e. the HOMC system returns 1.57 timesthe energy it consumes).

In the example of the CAES2 cycle, assuming it has the same expanderflow rate, the power delivery cycle is over at 1.3 hours, because thereis no provision in the CAES2 cycle to run at inlet pressures below 800psia (i.e. it is time to recharge the tank). In the HOMC cycle of thepresent embodiment, the expander cycle can continue to run until all ofthe air is driven out of the tank by the hydraulic fluid. The outputpower level of the CAES2 cycle is shown in Table 4, using the exact sameassumptions that outlined above for the HOMC cycle in Table 3. As can beclearly seen, the power output for the CAES2 system is reduced from 10MW to 6.8 MW and the time it can produce power is reduced from 4 hoursto 1.3, for a total energy output of 8.84 MWh. However, the total energyconsumption of the CAES2 system is also reduced, because the compressoronly has to charge the air storage from 800 psi to 1200 psi, which takesthe same power (6.92 MW from Table 1) as the HOMC cycle but only for1.48 hours (Table 2), or for a total energy input of 10.24 MWh input,yielding a “round-trip” cycle efficiency of 0.86 (8.84 MWh/10.24 MWh)for the CAES2 cycle.

TABLE 4 CAES2 Cycle Power Output CAES 2 - Expander WITHOUT Inter-stageheating - 1050° F. Exhaust Flow = 32 lbm/s T In T Out P In P Out P h Inh Out Δh Power Out Power Out Stage [° F.] [° F.] [pisa] [psia] Ratio[Btu/lbm] [Btu/lbm] [Btu/lbm] Btu/s MW 1 954 780 816 514 0.63 347 301 451452 1.53 2 780 574 514 273 0.53 301 249 52 1658 1.75 3 574 377 273 1300.48 249 201 49 1563 1.65 4 377 189 130 53 0.41 201 155 46 1458 1.54 5189 104 53 33 0.61 155 135 20 647 0.68 6 104 −11 33 15 0.45 135 107 28882 0.93 Σ 7660 8.08 84% Efficient Power Out MW 6.8

Table 5 shows a summary of the relative performance of the HOMC cycle vsthe CAES2 cycle given the same temperature access, the same air storagevolume, and the same expander cycle mass flow.

TABLE 5 Cycle Comparison Given Fixed Air Storage Volume (75,848 ft³⁾ andAccess to 1050° F. Heat Energy Round Trip Cycle Power Duration OutEnergy In Efficiency HOMC cycle 10 MW 4 hours  40 MWh 25.4 MWh 1.57CAES2 6.8 1.3 8.8 MWh 10.2 MWh 0.86

As can be clearly seen, the round trip electrical efficiency of the HOMCcycle is 1.8 times the efficiency of the CAES2 cycle, the total energyoutput of the HOMC cycle is 4.5 times the energy output of the CAES2cycle, and the HOMC cycle can sustain power production for 3 times aslong as the CAES2 cycle. As those skilled in the art will readilyappreciate, even if a hydraulic system similar to that used in thepresent embodiment were incorporated into the CAES2 cycle to pump all ofthe air out of the air storage, for the same mass flow the HOMC cyclehas a much higher power conversion, 10 MW, vs 6.8 MW, representing 1.5times as much power.

Where the energy storage and retrieval system of the present inventionwill be used in conjunction with a source of secondary heat, such as anexisting gas turbine, located on a navigable waterway, the presentinvention can be constructed on a barge at an offsite manufacturingfacility, as this is the most economical method to produce and packagethis system. Once the construction has been completed, the barge can befloated to the site of the gas turbine, anchored, and the necessaryconnections made to transfer secondary heat from the gas turbine to thepresent invention. Where the energy storage and retrieval system of thepresent invention will be used in conjunction with a secondary heatsource at a site not accessible by a navigable waterway, the presentinvention can be constructed at an offsite manufacturing facility withthe high pressure tanks preferably prefabricated in modules and theremaining system components mounted on one or more skids constructed sothat the entire energy storage and retrieval system can be transportedby barge to a port near the site, and then transported to site.

By contrast, existing CAES2 and SmartCAES systems have been constructedon-site, with each of the components built off-site and then shipped tosite where they are erected. For most of the components involved, theadditional costs incurred by on-site construction are relatively small,with the notable exception of the piping system. For example, when thepiping system is constructed at site, a welding process, an x-rayinspection process, a rework and re-inspection process and a finaltesting process need to be developed and executed in the field in orderto achieve the required pressure vessel approval under the standards ofthe American Society of Mechanical Engineers (“ASME”). If theseprocesses are executed in a controlled environment dedicated tomanufacturing, not only are costs reduced by avoiding local labor andnon-productive issues at site, but the ASME approval processes allow formore aggressive design which can result in thinner-walled piping,resulting in further cost savings. By constructing the present inventionon the same barge that it will permanently operate from, the entireenergy storage and retrieval system can be completed at themanufacturing facility with no critical welding in the field.

As those skilled in the art will readily appreciate, combined cyclepower plants have overall efficiencies that are so high that, there islikely not enough waste heat available to generate the amount of energythat would justify the cost of an HOMC system. Since the addition of anyparasitic power generation system (i.e. a system that requires thatadditional fuel be burned to generate additional power) to a combinedcycle power plant would likely reduce the overall efficiency of thepower plant more than simply burning that same amount of fuel via ductburners to add more heat to the heat recovery steam generator (“HRSG”)to produce more steam for the steam turbine, owners of such plantstypically do not add parasitic power generation systems to existingcombined cycle power plants. The total electrical energy that can beproduced by a combined cycle plant is typically limited by the generatorthat the gas and steam turbines drive, so that once the generatorreaches its limit, the burning of additional fuel will not produceadditional electrical power. Accordingly, if peak energy demands exceedthe generation capacity of a combined cycle plant, and the primary goalis to meet that peak demand, adding an HOMC system may be viable, evenif operated as a parasitic power generation system.

Accordingly, although the present invention has been shown and describedwith respect to an existing simple cycle gas turbine, the presentinvention can be incorporated into an existing combined cycle gasturbine power plant, as shown in FIG. 6. In this system, the secondaryheat provided to the present invention is received from the existingheat recovery steam generators (“HRSG”), and the second heat exchangecircuits can be supplied by tapping into the existing steam supply linesin parallel with one or more stages of the steam turbine. Whileobtaining secondary heat for the present invention in this manner willtend to reduce the overall efficiency of the steam turbine of thecombined cycle power plant, the power plant operator can modify theoperating profile of the combined cycle power plant to minimize any dropin power generation from the combined cycle gas and steam turbines inthose situations where the ability to generate electrical energy inexcess of that which can be produced by the generator of the combinedcycle power plant, or the ability to store compressed air energy formeeting a peak power demand, justifies such a reduction in overall dropin overall power plant efficiency. For example, many combined cyclepower plants have existing duct burners that can be fired to deliveradditional heat to the HRSG to provide additional steam to make up forthat steam that is diverted from the steam turbine supply lines to heatthe second heat exchange circuits of the plurality of heat exchangers.Alternatively, in-line burners could be added to provide heat, directlyor indirectly, to the second heat exchange circuit of the plurality ofheat exchangers of the HOMC to heat the compressed air as it flowsbetween expander stages. Likewise, the same type of HOMC system could beadded to the steam turbines used in coal-fired plants or nuclear plantsto provide additional power in times of peak demand, or to storecompressed air for future use in times of peak demand.

As those skilled in the art will readily appreciate, the presentinvention can be incorporated into other sources of secondary heat, suchas the exhaust gas of coal-fired power plants. The present invention canalso be incorporated into other heat sources such as the existing steamsupply of steam turbines in coal-fired, oil-fired or nuclear powerplants. Likewise, combustible gas byproducts, which are typically“flared” to dispose of them, or cleaned, dried and piped into a gaspipeline for sale, such as those produced by industrial processes likechemical plants, or biological processes like landfills, can be burnedto produce the secondary heat to be supplied to the second heat exchangecircuits of the heat exchangers of the present invention.

Additionally, the HOMC system of the present invention can be used withintermittent power producing systems such as solar, wind, wave and tidalpower generation systems that produce substantial amounts of electricalpower over long periods of time, but cannot be relied upon to producelarge amounts or electrical power to meet peak demands. When used inconjunction with these types of systems, the HOMC system can use powerproduced by the intermittent power producing systems to store compressedair in an air storage as described herein, while electrical heatingstrips or other heat generation mechanisms may be used to heat thecompressed air of the HOMC prior to entering the expander stages of theHOMC system.

FIG. 7 shows a schematic of the HOMC system of the present inventionintegrated into a photovoltaic solar plant. When the sun is shining, theoperator can make a decision on how much solar energy to use to run themotor to drive the compressor stages to store compressed air dependingon current and forecast market and weather conditions. The energy isstored in two forms: compressed air, and hot oil (like DowThermA®).Then, either during an intermittent period of sunshine or later in theday after the sun goes down, the HOMC expansion cycle is started toexpand the compressed air. The hot oil is used to provide additionalheat (“topping temperature”) to the compressed air after the pre-heaterbrings the temperature of the compressed air close to the temperature ofthe expander exhaust.

Advantageously, because the HOMC technology according to the inventioncan be built/installed directly on a barge, vehicle or other mobileplatform, as described earlier, other applications of the presentinvention can be used to maximize the benefit of intermittent powerwhere that power is produced in locations distant from demand, makingtransmission less efficient. For example, where there is an oversupplyof wind energy, such as in upstate New York, that energy could be storedas compressed air and used on a barge with a simplified HOMC system topower the refrigeration units that could ship fresh produce from thefarms of upstate New York to New York City (“NYC”), as well as to haulpost-consumer waste material (e.g., food waste, food production waste orother biofuel or biogas waste) from NYC to one or more remote locations.

FIG. 10 shows how the cycle would work. Initially the HOMC barge wouldbe loaded in upstate New York with shipping containers full of produce,while at the same time, wind energy would be used to run an electricalcompressor to charge high pressure tanks in the barge. At the same time,natural gas could also be compressed and stored on the barge.

In this application, it is estimated that approximately 400 kw of energyis needed to keep the produce properly refrigerated during transport,energy that can be supplied by a small gas turbine, referred to as a“micro turbine”, of the type commercially available from CapstoneTurbine Corporation. The invention allows this micro turbine to bemodified to remove the compressor and increase the generator capacity.For example, the Capstone micro turbine is a single stage compressor,single shaft, single combustor and single turbine system that drives a200 kw generator. Approximately half of the power generated by theturbine is consumed by the compressor. By removing the compressor, thatload also is removed, so the full turbine power, approximately 400 kw,can be used to drive a larger, 400 kw generator providing greaterefficiencies. During transport, the compressed air and the compressednatural gas onboard the barge are regulated and supplied to the microturbine, and the HOMC system is preferably sized so that preferably,about half the compressed natural gas is consumed but only a smallportion of the compressed air is consumed. Once the barge gets to NYC,the produce is off-loaded and waste containers with post-consumer foodwaste material are loaded onto the barge. The barge, still filled withthe majority of compressed air, then travels a distance (preferably ashort distance) to a local gas turbine power plant, such as the onelocated at Astoria, N.Y.

At the gas turbine power plant, during periods where additional power isnot required, the compressed air can be released from the tanks on thebarge, preheated with the balance of compressed natural gas left on thebarge, and injected into the power plant gas turbine downstream of thecompressor to reduce the fuel burn (improve the efficiency and reducethe emissions) of the gas turbine while maintaining plant output. Inthis case, the gas turbine compressor mass flow is reduced by closingthe inlet guide vanes slightly and the preheated air replaces the massflow caused by closing slightly the inlet guide vanes. During peak powerload periods, the compressed preheated air from the barge can be usedinstead to add flow to the gas turbine (i.e., the mass flow through thecompressor is not reduced by closing the inlet guide vanes), thusproviding power augmentation while at the same time improving theefficiency and reducing the emissions of the gas turbine power plant.When the compressed air tanks on the barge are empty (i.e. the pressurefalls below the pressure of the working fluid in the gas turbine wherethe compressed air is to be injected), the barge heads back upstate.

The containers with the post-consumer waste material (e.g., food or foodproduction waste or other biofuel/biogas) are then delivered to a remotesite where the containers are off-loaded and either hauled away, or usedin a bio-digester to make biofuel/biogas that can be used either on thebarge in lieu of using compressed natural gas (e.g. to run the microturbine refrigeration system, preheat the air for the gas turbine powerplant) or optionally used to power the tugboat that is pushing thebarge.

In order to avoid the additional shipping costs of trucking shippingcontainers from their destinations back to their source location wherethey can be used again (i.e., getting empty produce containers backupstate and getting the empty waste containers back to NYC), theshipping containers could be special foldable containers, of the typeknown in the art, where multiple containers, when folded, will fit inthe place of one. This would allow two sets of shipping containers toused be on the same barge at the same time, one for produce and one forwaste products, with one set always folded. In this application, thebarge would head for NYC with shipping containers full of produce aspreviously described. Once the barge gets to NYC, the shippingcontainers with the produce are offloaded, and empty, folded shippingcontainers for produce are loaded onto (and stored) on the barge. Thebarge then continues on to where it the shipping containers full ofpost-consumer food waste material are located. There, empty, foldedshipping containers for post-consumer food waste material areoff-loaded, and shipping containers full of post-consumer food wastematerial are loaded onto the barge. When the barge arrives at thedestination for the post-consumer food waste material, the shippingcontainers with the post-consumer food waste material are offloaded, andempty, folded shipping containers for post-consumer food waste materialproduce are loaded onto (and stored) on the barge. The barge thencontinues on upstate to where the shipping containers full of produceare located, where the empty, folded shipping containers for produce areoff-loaded, and shipping containers full of produce are loaded onto thebarge to start the shipping cycle all over again.

Note that if biofuel is not used in the shipping cycle just described,(or not used in the initial implementation of the shipping cycle),natural gas can be compressed using the same wind power as thecompressed air is using, thus capturing otherwise wasted wind energy andputting it to useful work. In this case, the air compression equipmentand natural gas compression equipment would be located near each otherat the upstate terminal location where the shipping containerscontaining the produce are loaded on the barge. Such an application ofthe present invention would have the benefit of reduced cost of produceor other consumable products (due to lower shipping costs), reducedoverall emissions, and reduced truck traveling on congested roadways inand out of the NYC. In addition, since the present invention provides ameans or system for storing and producing energy at a much lower costper kilowatt-hour than other available technologies, and since otherrevenue streams are added (including hauling garbage out of the NYC andusing stored energy to produce energy in or near NYC, for example), thepresent invention effective uses wind energy that might otherwise not beuseable in a transmission-constrained city such as NYC. Although thisapplication of the present invention has been described as used withwind power, it is to be understood that it could be used similarly withother intermittent energy sources (e.g., tide-based, hydraulic, solar,biofuel/biogas, etc.), or it could be used with power from the grid,used at times of low energy demand (i.e. off-peak power), to compressthe air and natural gas stored on the barge. Likewise, this applicationis described in terms of using natural gas or biofuel, if the biofuel isin the form of biogas, the same intermittent or off-peak power could beused to compress and store biogas in the tanks on the barge.

Accordingly, another aspect of the invention relates to methods andsystems for transporting or shipping goods, preferably refrigerated orfrozen goods, using one or more CAES systems, preferably a HOMC systemaccording to the invention, preferably built or otherwise installed onthe transportation platform (e.g., barge, ship, rail, etc.).

One embodiment relates to methods and systems comprising atransportation vehicle comprising at least one refrigeration unit atleast partially powered by a CAES system (directly or indirectly),preferably a HOMC system according to the invention.

Preferably, the transportation vehicle is a barge, rail car, ship, truckor aircraft.

Preferably, the one or more CAES systems are secured or built onto orwithin the transportation vehicle.

According to preferred methods, the CAES system is stored with energygenerated at a first location and the stored energy is used to power therefrigeration unit(s) while the transportation vehicle travels to asecond location. Preferably, energy generated by wind, solar, waves,tide, hydraulic or other renewable energy or excess energy is stored inthe CAES systems.

According to preferred embodiments, the method further comprisestransporting post consumer food or other biofuel waste products from awaste generating location to a biofuel using location. Preferably, themethod further comprises using the post consumer food or other biofuelwaste products to generate energy for the refrigeration units, the CAESsystem(s), the transportation vehicle and/or for use at a biofuel siteor power plant site.

According to one preferred embodiment, wind energy or other renewableenergy or excess energy is employed to run an electrical compressor tocharge high pressure tanks on the transportation vehicle. Thisadvantageously allows the compressor unit to be omitted from the gasturbine that provides energy to the refrigeration unit on the vehiclethus reducing the weight and the energy consumption (since thecompressor typically consumes about 50% of the energy).

According to another preferred embodiment, the renewable energy chargesat least one high pressure air tank and at least one high pressurenatural gas tank. Preferably, the high pressure air and high pressurenatural gas is supplied to the gas turbine for the refrigeration unitduring the transport. Preferably, during transport less than 50% of thecompressed natural gas is consumed, while less than 25%, preferably lessthan 10% of the compressed year is consumed. Preferably, afterdelivering the goods, the remaining natural gas is used the heat thecompressed air and the heated compressed air is supplied to a gasturbine power plant to improve efficiency and/or reduce emissions.

According to another embodiment, the transportation system comprises (a)a transportation vehicle; (b) a refrigeration system; and (c) at leastone compressed air storage system for providing energy, directly orindirectly, to the refrigeration system. Preferably, the system furthercomprises (d) at least one compressed natural gas storage systems forproviding energy, directly or indirectly, to the refrigeration system.Preferably, the system comprises one or more sets of containers for thegoods, preferably collapsible or foldable containers. According toparticularly preferred embodiments, the system comprises one or moreshipping containers for consumable products and one or more shippingcontainers for biofuel waste products. Preferably, the system comprisesa CAES system, preferably a HOMC system according to the invention.

Another embodiment relates to a method of transporting consumableproducts comprising:

(a) charging one or more gas storage systems installed or built orlocated on a vehicle using renewable energy or excess energy;

(b) transporting said consumable products from a first location to asecond location,

wherein said one or more gas storage systems provides energy torefrigerate the consumable products during the transportation.

Preferably, the method comprises charging at least one air containersystem with air and at least natural gas container system with naturalgas.

Preferably, the method further comprises using the at least one gasstorage system to provide energy or increased efficiency to at least onepower plant.

Preferably, the method further comprises transporting and supplyingbiofuel or biogas to at least power plant. Preferably, the consumableproducts and the biofuel or biogas products are transported in differentcontainers, preferably wherein the containers can be folded or collapsedon the vehicle when not in use. According to preferred embodiments, thebiofuel containers are collapsed or folded while the consumable productsare being transported and the consumable products containers arecollapsed or folded while the biofuel is being transported. Thisadvantageously allows a single transportation vehicle to transport bothtypes of products during different legs of its transportation cycle.

Furthermore, as demand for electrical power has increased, gridcontrolling authorities have placed a higher value on fast respondinggeneration, called “regulation”, because the amount of intermittentgeneration, such as that from solar, wind, and waves, has beenincreasing and because intermittent generation can suddenly increase ordecrease in output due to rapid changes in the environment. Power plantsget paid more for regulation, and all assets being paid for asregulation are synchronized to the grid and are running at part load.The amount of regulation that power plants can sell is limited to theamount of output they can change within 10 minutes of receiving arequest from the power grid. Currently, “energy batteries”, which canrespond to demand from the grid in milliseconds, are serving thismarket. As used herein, the term “energy battery” or “energy batteries”mean chemical batteries, capacitors, flywheels, and similar energystorage devices that can deliver additional electrical powerinstantaneously (i.e. within milliseconds rather than within seconds orminutes) in response to grid demand. However, energy batteries arelimited in that they are energy neutral devices. For example, a 1 MWchemical battery typically has 1 hour of storage and is on the system athalf charge, so that it can absorb 0.5 MW for up to one hour anddischarge 0.5 MW for up to one hour. Battery systems typically have anAC-to-AC round trip efficiency of not more than 80%, therefore, on theenergy absorption mode, it actually takes in 1.2 times as much energy tocharge the battery as it returns when it discharges, or 0.6 MWh absorbedfor every 0.5 MWh that it puts out. (This is routinely called “energyneutral” but in reality, it is not) These systems have a similar costper MW as a HOMC system, however, for the same cost per MW, the HOMCsystem is designed to deliver energy for at least 4 hours and thus costone-fourth of the cost of a chemical battery on a per MWh basis.

One advantage of CAES type systems is that they are inherently able toquickly change load by simply opening or closing flow control valves. Agas turbine, by comparison, typically can meet a requested grid load(“load follow”) but with up to a five minute delay, whereas a CAES typeplant has the ability to change load in 10 seconds and it can deliverhours (typically at least four hours) of energy, depending on the massof compressed air that can be stored in the air storage. Consequently,when a very small battery is incorporated in the HOMC system of thepresent invention, the result is an energy storage and retrieval systemthat can deliver regulation on a millisecond basis, just like a chemicalbattery, but rather than being energy neutral, can deliver more energyto the grid than it consumes if the secondary heat is waste heat whichis not accounted for in the compression cycle of the HOMC of the presentinvention.

An example of how a HOMC system could be used in a regulation mode, ascompared to a battery, is shown in FIG. 8. Initially, the grid is stableat 5 MW at time zero, and the automatic grid control (“AGC”) signalvaries up and down 0.5 MW. The AGC signal can be changed every sixseconds, so that often a gas turbine will not have reached the onerequested output setpoint before the signal is again changed to anotheroutput setpoint. Being much faster, energy batteries will probably havereached the new setpoint within the six seconds between AGC signaloutput requests, and as such they are said to have “perfect regulation”.For example, a chemical battery with a power rating of 1 MW for 1 houris able to follow this demand curve, as is the HOMC with a 1 MW powerrating, for 30 seconds. At 15 seconds, shown as point “A” in FIG. 8, theAGC gives a command to increase the power level to 10 MW. The HOMCsystem can follow that command exactly by ramping the mass flow ofcompressed air from half flow (5 MW) up to full flow 10 MW. The batterycan contribute 0.5 MW, but falls short of being able to ramp to the 10MW load request, since the battery would have to be ten times larger(and presumably ten times the cost) to meet the 10 MW demand from theAGC. By comparison, the gas turbine in this example takes about 5minutes to ramp up to the 10 MW load (315 seconds). While the gasturbine may be able to ramp up by 10 MW in less than the 5 minutes shownin this example, it certainly cannot do so within the 6 second periodbetween successive AGC signals.

FIG. 9 is a schematic drawing showing how the HOMC cycle would operateif the heat exchangers used in the present embodiments were replacedwith direct fired combustors. This allows the HOMC system to beinstalled without the use of waste heat. In this application, the HOMCsystem extracts almost all of the heat added in the combustion processby transferring most of the expander exhaust energy to the air comingfrom the air tank in the pre heater. While not as efficient as when itoperating with waste heat (where the cost of the waste heat isconsidered to be zero), an HOMC operating with direct fired combustorshas overall thermal cycle efficiencies approaching those of moderncombined cycle power plants.

As those skilled in the art will readily appreciate from the foregoing,the use of high pressure air storage tanks in conjunction with theinter-stage reheating of the compressed air in the expansion circuitsubstantially reduces the required volume of the air storage, andtherefore the cost of that air storage, while also making the HOMCtransportable and relocatable, and avoiding the costs of acquiring landto site additional generating capacity. Likewise, the use hydraulicfluid to maintain the pressure of the compressed air in the air storageas the mass of the compressed air in the air storage is reduced duringoperation of the HOMC expansion cycle, also reduces the required volumeof the air storage. Since the cost of the air storage is often more thanhalf of the cost of a typical CAES system in those cases where a cavernis not available for use as air storage, the HOMC of the presentinvention provides energy storage and retrieval at a cost that iscompetitive with other options available to power authorities. Whenwaste heat is used to heat the compressed air between expander stagesduring the expansion cycle, the HOMC of the present embodiment iscost-competitive as compared with other options while meeting currentemissions requirements, and can provide more energy (MWh) to theelectrical grid than is consumed during the storage process, where thecost of producing the waste heat is considered to be zero. In addition,the nature of the present embodiment allows it to be combined withintermittent power generation to provide electrical power in response todemand, and when combined with energy batteries, the present embodimentcan provide response times similar to energy batteries for substantiallylonger periods of time at substantially lower costs, than using anenergy battery by itself.

It should be clear that the HOMC of the present invention is useful forcapturing secondary heat from many commonly available sources, asdisclosed herein. Those skilled in the art will readily appreciate thatthe HOMC is not limited to the types of installations sites thattraditional CAES systems (e.g. SmartCAES, CAES2) are restricted to dueto their size. Since the HOMC of the present invention requiressubstantially less air storage volume than such CAES systems, the HOMCcan be installed in places, (e.g. basements of buildings) to make use ofsecondary heat produced by the equipment already in place, to generatepower that can be used by the building, its tenants, or sold to thegrid.

While the invention has been described in what is known as presently thepresent embodiment, it is to be understood that the invention is not tobe limited to the disclosed embodiment but, on the contrary, is intendedto cover various modifications and equivalent arrangements within thescope of the following claims.

1. An energy storage and retrieval system for obtaining useful work froman existing source of secondary heat, said system comprising: a sourceof compressed air; at least one generator; a plurality of expanderstages, each of said plurality of expander stages having an inlet and anoutlet, at least a portion of said plurality of expander stages havingan outlet flow control, and each of said plurality of expander stagesconnected to said at least one generator; a first manifold; and a firstplurality of heat exchangers, including an initial heat exchanger and afirst plurality of downstream heat exchangers, each of said firstplurality of heat exchangers having a first heat exchange circuit and asecond heat exchange circuit; wherein each of said first heat exchangecircuits of said first plurality of downstream heat exchangers is inselective fluid communication with one of said outlets of said pluralityof expander stages through one of said outlet flow controls of saidplurality of expander stages, and each of said second heat exchangecircuits of said first plurality of heat exchangers is in fluidcommunication with said first manifold, and said first manifold is influid communication with said source of secondary heat to receivesecondary heat therefrom.
 2. The energy storage and retrieval system ofclaim 1 further comprising a second manifold, a pre-heater heatexchanger having a first heat exchange circuit and a second heatexchange circuit, wherein said first circuit of said pre-heater heatexchanger is in fluid communication with said second manifold and saidsource of compressed air, and said second heat exchange circuit of saidpre-heater heat exchanger is in fluid communication with one of saidoutlets of said plurality of expander stages to receive said compressedair therefrom.
 3. The energy storage and retrieval system of claim 2further comprising a source of coolant with an outlet and an outlet flowcontrol; wherein, said generator is a combined motor/generator, saidsource of compressed air includes an air storage, and a plurality ofcompressor stages driven by said motor/generator, including an initialcompressor stage and a plurality of downstream compressor stages, eachof said plurality of compressor stages having an inlet and an outlet,each of said plurality of downstream compressor stages having an inletflow control, and at least a portion of said plurality of compressorstages having an outlet flow control, and a third manifold in fluidcommunication with said air storage, said third manifold having aplurality of inlets, each of said plurality of inlets of said thirdmanifold having an inlet flow control, and each first heat exchangecircuit of said first plurality of heat exchangers is in selective fluidcommunication with one of said inlets of said plurality of downstreamcompressor stages through one of said inlet flow controls of saidplurality of downstream compressor stages, in selective fluidcommunication with one of said plurality of inlets of said thirdmanifold through one of said inlet flow controls of said third manifold,and in selective fluid communication with one of said outlets of saidportion of said plurality of compressor stages through one of saidoutlet flow controls of said portion of said plurality of compressorstages, and each second heat exchange circuit of said first plurality ofheat exchangers is in selective fluid communication with said outlet ofsaid source of coolant through said outlet flow control of said sourceof coolant.
 4. The energy storage and retrieval system of claim 3wherein said source of secondary heat includes an outlet and an outletflow control, said first manifold includes a plurality of outlets andoutlet flow controls, each of said inlets of said plurality of expanderstages includes an inlet flow control, and each first heat exchangecircuit of said first plurality of heat exchangers is in selective fluidcommunication with one of said inlets of said plurality of expanderstages through one of said inlet flow controls of said plurality ofexpander stages and in selective fluid communication with said secondmanifold through with one of said outlet flow controls of said secondmanifold, and each second heat exchange circuit of said first pluralityof heat exchangers is in selective fluid communication with said outletof said source of secondary heat through said outlet flow control ofsaid source of secondary heat.
 5. The energy storage and retrievalsystem of claim 4 wherein each of said inlet flow controls and outletflow controls are independently operable to provide a first operatingcondition in which said plurality of expander stages is fluidly isolatedfrom said first plurality of heat exchangers and each of said firstplurality of heat exchangers is in fluid communication with at least oneof said plurality of compressor stages, and a second operating conditionin which said plurality of compressor stages is fluidly isolated fromsaid first plurality of heat exchangers and each of said first pluralityof heat exchangers is in fluid communication with at least one of saidplurality of expander stages.
 6. The energy storage and retrieval systemof claim 5 further including a source of hydraulic fluid, and flowcontrol in fluid communication with said source of hydraulic fluid andsaid air storage for selectively permitting transfer of said hydraulicfluid into said air storage as the mass of compressed air in the airstorage is reduced to maintain the pressure of said compressed air insaid air storage at a predetermined level, and selectively permittingtransfer of said hydraulic fluid from said air storage as the mass ofsaid compressed air in said air storage is increased.
 7. The energystorage and retrieval system of claim 6 further including a hydraulicpump in fluid communication with said source of hydraulic fluid and saidair storage for pumping said hydraulic fluid into said air storage asthe mass of compressed air in the air storage is reduced to maintain thepressure of said compressed air in said air storage at a predeterminedlevel.
 8. The energy storage and retrieval system of claim 6 whereinsaid source of secondary heat is a gas turbine.
 9. The energy storageand retrieval system of claim 6 wherein said source of secondary heat isan industrial process.
 10. The energy storage and retrieval system ofclaim 6 wherein said source of secondary heat is a steam turbine. 11.The energy storage and retrieval system of claim 6 wherein said systemis modular and can be transported in preassembled components to beassembled at the site of said source of secondary heat.
 12. The energystorage and retrieval system of claim 6 wherein said system is assembledon a mobile platform and transported to the site of the source ofsecondary heat to be connected in fluid communication with said sourceof secondary heat.
 13. The energy storage and retrieval system of claim6 wherein said system further includes an energy battery to provideinstantaneous electrical power to provide energy at a predeterminedlevel of power until said generator generates electrical power at saidpredetermined level of power.
 14. The energy storage and retrievalsystem of claim 6 wherein said motor/generator that drives saidcompressor stages is powered by an intermittent power producing system.15. The energy storage and retrieval system of claim 2 furthercomprising a source of coolant; a third manifold having a plurality ofinlets, a fourth manifold having a plurality of outlets, a secondplurality of heat exchangers, including a second plurality of upstreamheat exchangers and a final heat exchanger, each of said secondplurality of heat exchangers having a first heat exchange circuit and asecond heat exchange circuit; wherein, said generator is a combinedmotor/generator, said source of compressed air includes an air storagein fluid communication with said third manifold, and a plurality ofcompressor stages driven by said motor/generator, including an initialcompressor stage and a plurality of downstream compressor stages, eachof said plurality of compressor stages having an inlet and an outlet,and a flow control controls flow into the inlet of each of saidplurality of downstream compressor stages, wherein each of said firstheat exchange circuits of said second plurality of upstream heatexchangers is in fluid communication with one of said outlets of saidplurality of compressor stages, and each of said second heat exchangecircuits of said second plurality of heat exchangers is in fluidcommunication with said first manifold, and said first manifold is influid communication with said source of secondary heat to receivesecondary heat therefrom, and each first heat exchange circuit of saidsecond plurality of heat exchangers is in selective fluid communicationwith one of said inlets of said plurality of downstream compressorstages through one of said flow controls that control flow into theinlet of each of said plurality of downstream compressor stages, influid communication with one of said plurality of inlets of said thirdmanifold, and in fluid communication with one of said outlets of saidportion of said plurality of compressor stages, and each second heatexchange circuit of said first plurality of heat exchangers is in fluidcommunication with said source of coolant.
 16. The energy storage andretrieval system of claim 15 wherein said first manifold includes aplurality of outlets and outlet flow controls, and each first heatexchange circuit of said first plurality of heat exchangers is in fluidcommunication with one of said inlets of said plurality of expanderstages and in selective fluid communication with said second manifoldthrough with one of said outlet flow controls of said second manifold,and each second heat exchange circuit of said first plurality of heatexchangers is in selective fluid communication with said source ofsecondary heat.
 17. The energy storage and retrieval system of claim 16further including a source of hydraulic fluid, wherein said air storageis in fluid communication with said source of hydraulic fluid to allowtransfer of said hydraulic fluid into said air storage as the mass ofcompressed air in the air storage is reduced to maintain the pressure ofsaid compressed air in said air storage at a predetermined level and toallow transfer of said hydraulic fluid from said air storage as the massof said compressed air in said air storage is increased.
 18. The energystorage and retrieval system of claim 17 further including a hydraulicpump in fluid communication with said source of hydraulic fluid and saidair storage for pumping said hydraulic fluid into said air storage asthe mass of compressed air in the air storage is reduced.
 19. The energystorage and retrieval system of claim 18 wherein said source ofsecondary heat is a gas turbine.
 20. The energy storage and retrievalsystem of claim 18 wherein said source of secondary heat is anindustrial process.
 21. The energy storage and retrieval system of claim18 wherein said source of secondary heat is a steam turbine.
 22. Theenergy storage and retrieval system of claim 18 wherein said system ismodular and can be transported in preassembled components to beassembled at the site of said source of secondary heat.
 23. The energystorage and retrieval system of claim 18 wherein said system isassembled on a mobile platform and transported to the site of the sourceof secondary heat to be connected in fluid communication with saidsource of secondary heat.
 24. The energy storage and retrieval system ofclaim 18 wherein said system further includes an energy battery toprovide instantaneous electrical power to provide energy at apredetermined level of power until said generator generates electricalpower at said predetermined level of power.
 25. The energy storage andretrieval system of claim 18 wherein said motor/generator that drivessaid compressor stages is powered by an intermittent power producingsystem.
 26. A method for obtaining useful work from an existing sourceof heat, said system comprising: providing a source of compressed air;providing a plurality of expander stages, each of said plurality ofexpander stages connected to at least one generator; extracting work byreleasing compressed air from said source of compressed air,transferring heat from said source of heat to said compressed air priorto said compressed air entering each of said plurality of expanderstages; and, expanding said compressed air through said plurality ofexpander stages to drive said at least one generator.
 27. The method ofclaim 26 wherein the step of further including the step of extractingwork by releasing compressed air from said source of compressed air, isfollowed by the step of maintaining the pressure of said compressed airin said source of compressed air at a predetermined level bytransferring a hydraulic fluid into said air storage as releasing ofcompressed air is occurring.
 28. An energy storage and retrieval systemfor obtaining useful work from a source of heat, said system comprising:means for producing compressed air; means for storing said compressedair; means for extracting work from said compressed air including aplurality of expanders, a plurality of first conduits, and a pluralityof second conduits, each of said expanders having an inlet and anoutlet, each of said first conduits connected to one of said inlets ofsaid plurality of expanders to deliver said compressed air thereto, andeach of said second conduits connected to one of said outlets of saidplurality of expanders to receive said compressed air therefrom; and,means for transferring energy between said compressed air and a heattransfer fluid, including a first manifold, and a first plurality ofheat exchangers, including an initial heat exchanger and a plurality ofdownstream heat exchangers, each of said first plurality of heatexchangers having a first heat exchange circuit including a first inletand a first outlet, and a second heat exchange circuit including asecond inlet and a second outlet, each of said first outlets of saidfirst plurality of heat exchangers connected to one of said firstconduits to deliver said compressed air thereto, each of said firstinlets of said plurality of downstream heat exchangers connected to oneof said second conduits to receive said compressed air therefrom, andeach of said second inlets of said plurality of heat exchangersconnected to said first manifold; wherein said energy is heat from saidsource of heat, and said first manifold is connected to said source ofheat to receive said heat transfer fluid therefrom for transferring saidenergy to said compressed air.